# Brain Teaser



## 2500Ram

This was posted on a different board and there has been good debate on both sides, it's about a 50 50 split, your opnion...

Bill.

*** Brain Teaser ***

Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation. 
There is no wind.

Can the plane take off?


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## nascarcamper

My guess would be if the conveyor belt was moving in the opposite direction of the wheel at the same speed then the plane would not be moving therefore no wind would be going across the wings so it would be impossible to take off. Or am I missing something?


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## 2500Ram

That's my thought as well but there will be others to say it will take off.

Just wait


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## Steelhead

I agree. No movement of the aircrft's body or wings and therefore no lift. must have air movement over the airfoils to create lift.









Dallas


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## skills4lou

This one's easy guys: the wheels aren't what give the plane forward thrust. It's the prop or jet. It doesn't matter what speed the wheels are or aren't turning. So, if the only variable is that the wheels aren't spinning (and otherwise the plane would take off, ie sufficient thrust and lift) then it will take off.


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## ee4308

I agree also. Always thought there had to be a wind force factor to get it airborn.
Just my $.02 worth though.


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## nascarcamper

skills4lou said:


> This one's easy guys: the wheels aren't what give the plane forward thrust. It's the prop or jet. It doesn't matter what speed the wheels are or aren't turning. So, if the only variable is that the wheels aren't spinning (and otherwise the plane would take off, ie sufficient thrust and lift) then it will take off.
> [snapback]65907[/snapback]​


If that's the case how do gliders get airborne? No prop or jet. If the conveyor and wheels are going the same speed no movement = no lift. The purpose of the jet or prop is to cause movement right?


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## CTRNAVRET

skills4lou said:


> This one's easy guys: the wheels aren't what give the plane forward thrust. It's the prop or jet. It doesn't matter what speed the wheels are or aren't turning. So, if the only variable is that the wheels aren't spinning (and otherwise the plane would take off, ie sufficient thrust and lift) then it will take off.
> [snapback]65907[/snapback]​


Where is the lift if the wings are not moving thru the air? If the conveyor is running the same speed OPPOSITE the wheels then the aircraft is not moving thru the air therefore no lift







Carl


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## CamperAndy

OK guys the thrust of the jet or prop does not act on the wheels it acts on the air and would cause the plane to move irrespective of the wheel speed.


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## CamperAndy

nascarcamper said:


> skills4lou said:
> 
> 
> 
> This one's easy guys: the wheels aren't what give the plane forward thrust. It's the prop or jet. It doesn't matter what speed the wheels are or aren't turning. So, if the only variable is that the wheels aren't spinning (and otherwise the plane would take off, ie sufficient thrust and lift) then it will take off.
> [snapback]65907[/snapback]​
> 
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> If that's the case how do gliders get airborne? No prop or jet. If the conveyor and wheels are going the same speed no movement = no lift. The purpose of the jet or prop is to cause movement right?
> [snapback]65917[/snapback]​
Click to expand...

There is a tow plane that does have an engine.


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## 2500Ram

Let the debate begin. 
This was over 70 replies in 2 days on the other board. I'm still not sure on the answer but everything being equal with no movement, 0 mph from the plane there can be no lift, now the wheels don't create the thrust so it's possible that the plane is moving faster air speed to the treadmill causing lift


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## nascarcamper

Unless it's a Harrier jump jet I get on it because I don't fly.


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## nascarcamper

CamperAndy said:


> nascarcamper said:
> 
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> skills4lou said:
> 
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> 
> This one's easy guys: the wheels aren't what give the plane forward thrust. It's the prop or jet. It doesn't matter what speed the wheels are or aren't turning. So, if the only variable is that the wheels aren't spinning (and otherwise the plane would take off, ie sufficient thrust and lift) then it will take off.
> [snapback]65907[/snapback]​
> 
> 
> 
> If that's the case how do gliders get airborne? No prop or jet. If the conveyor and wheels are going the same speed no movement = no lift. The purpose of the jet or prop is to cause movement right?
> [snapback]65917[/snapback]​
> 
> Click to expand...
> 
> There is a tow plane that does have an engine.
> [snapback]65920[/snapback]​
Click to expand...

That's my point. It's not the thrust or airflow from the propulsion system going across the wings that make them lift. Jet flow is behind the wings and prop wash is equally dispersed. It's just a means of propulsion since you can't drive it by wheels when in the air.


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## Thor

The plane would not take off - No motion forward = no lift.

It really does not matter what supplies the trust, wheels or engine, the plane will not move forward unless the wheels are turning faster than the conveyor belt. Since in this example that is not possible the plane will not move forward.

It is like pushing against a wall; nothing moves because all forces are balanced. The force you push againsts = the force the wall is pushing back on you.

The plane thrust = the force of the conveyor belt moving in the opposite direction.

Thor

Now if a tree falls in a forest with no one around to hear it, does it make a sound?


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## CamperAndy

One more try here.

The engine does not turn the wheels of a plane. So unless the engine causes the plane to move forward because of the thrust generated there will be no need for a conveyor belt. But since the plane is being thrusted forward there will be lift generated. The belt will now spin but will not prevent the plane from moving.

Remember the belt is the size of a runway and how often does a plane need more then the length of a runway to take off.


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## PDX_Doug

The plane will indeed takeoff, as it will accelerate relative to the air around it to a speed sufficiant to create enough lift to takeoff (all else being equal).

Andy is on the right track here, but there is another factor that needs to be considered, and it is what makes this a brain teaser. That is the whole notion of the 'moving conveyor belt' runway. The mistake is to visualize this runway in terms relative to the ground around it. You must instead, visualize it relative to the motion of the plane, and in that light, a normal 'fixed' runway is - relative to the aircraft - moving at the speed of the airplane tires and in the opposite direction. You do not need a moving belt to achieve this... every runway on the planet (sans an aircraft carrier flight deck) achieves this relative motion.

Don't see it? Look out the window at the runway the next time you are on an airplane during it's takeoff roll. Relative to your vantage point on the plane, it is moving backwards. And the faster the plane moves, the faster the runway seems to be moving backwards as well.

What great mind benders on this year, the 100th anniversary of Einstein's General Theory of Relativity!









Now what would that airplane look like if you were sitting on a beam of light?...

Happy Trails,
Doug


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## Moosegut

If there is no air movement over and under the wings - it stays on the ground. The shape of the wing is what makes it aerodynamic, not the rotation of the wheels. The forward motion of the plane forces air to move over the wing at a different rate than the air under it, thus providing lift. Same thing with a glider - it's the forward motion that sends air over and under the wings, but it doesn't necessarily have to be forward motion. Take a glider to Kill Devil Hills, NC and place it on top of a dune. If the wind causes air to rush over and under the leading edge of the wing, it may very well take off due to the wind.

The Harrier lifts vertically because of the engine thrust. But, the engines slowly turn to give it the forward thrust that provides the air movement across the wings. Glide ratios are different for each plane due to many factors - weight, wing span etc. Kill the engine in mid-air and you'll see how far you can glide - don't try that one at home. But, all fixed-wing aircraft have SOME glide cabability - it may only be a few feet before it starts dropping lick a rock. The forward thrust provided by the engines provide the proper AIR SPEED for each aircraft across the wings to provide the lift.

At least, that's what my dad used to tell me when he took me flying in his plane. I was really the only one who ever went with him as a kid - I loved it. That was back in the days when we used to be able to buzz the house and all the family and neighbors would come out in the yard and shine mirrors at us. Wow! I haven't thought about that in years! Yikes - decades!









My 2 cents.

Scott


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## HootBob

I say it will not
There is no air pressure to lift the plane.

Man it's to early to think about something like this









Don


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## summergames84

You guys are giving me a headache...like Hootbob, it is too early in the AM to think this hard. I think I'm ruined for the day...









Should we start another thread about trees falling in the woods??


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## tdvffjohn

I don t like to fly so I don t care whether it does or not









John


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## Crawfish

The plane will take off.
I called my son who is an areo-space engineer and he told me more or less the same thing Doug said. The thrust from the engines will propell the plane forward creating lift, the wheels are just for steering and less friction to the ground.

Let's get back to a good brain teaser about the tree in the woods. My answer to this one is simple. Sound is waves moving through the air. You can't see them. To know they are there, you have to have a device detect them, ears, radios, etc. If you don't have that device, then you can't hear them. Hince, if a tree falls in the woods and there is no device to receive the sound waves, there is no sound.

"*Let's Go Camping*"

Crawfish


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## Moosegut

Crawfish said:


> if a tree falls in the woods and there is no device to receive the sound waves, there is no sound.
> 
> "*Let's Go Camping*"
> 
> Crawfish
> [snapback]65962[/snapback]​


Oh, you're really gonna start trouble with that one!









Just because there is no "device" to receive the sound waves does not mean the sound waves are not there. The sound waves are still produced in the air (now, a vacuum is a horse of a whole different story







), there's just no "device" to collect or detect them.

We "detect" sunlight with our eyes. When we close our detection devices (our eyes) the sunlight is still there. When we are on the dark side of the earth at night, the sun still shines on the other side even though our "detectors" are not there. Now, the light in the Good Humor truck - I'm not so sure about that.









When there is an earthquake under the ocean, there my be no device in the area to detect that, but those shock waves (the rings of water) still travel out from the source that created them. Same as sound waves.

We may have to consult Bill Nye as the final arbiter on this one.


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## GlenninTexas

If you are carrying 1000 lbs of canaries in your Outback and they all simultaniously take off and fly, does it lower the weight you are towing?


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## PDX_Doug

One more thought on this airplane thing (before we move onto trees in the woods)...

For those of you that do not believe the aircraft will take off, since the plane is not in motion, and there is no air movement across the wings, and thus no lift, consider this:

1. The wheels on the plane are not powered. that is to say they turn (roll) only when there is forward motion of the airplane (again, relative to the runway). There is not an aircraft in the world with powered wheels*.

2. Also, as the question was posed, the conveyor belt runway is designed to move in the opposite direction of the wheels, and at the same speed.

Those two points leave us with this: The runway only moves in reaction to the turning wheels. The wheels only turn if there is forward motion of the airplane. However, according to what many of you are arguing, the plane will not move forward. And if it is not moving forward, the wheels will not turn, and the conveyor belt will not move, in which case the plane can move forward, except that then the wheels will turn, which will cause the conveyor to move, which will stop the forward motion of the airplane, which will cause the wheels to stop turning, which will...

In other words, the belt can only move if the plane is moving, and the plane can not move if the belt is moving.

What we have here, is what computer programmers refer to as Circular Reference. In other words, the equation cannot be resolved. Thus, the basic premise of the question is misleading.

Too early in the morning for this? Hey, this is the kind of good stuff that gets the old noggin working!









Happy Trails,
Doug

* We will ignore the whole flying car thing here!


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## nascarcamper

All I know is when I walk on my treadmill I don't get a breeze in the face.


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## nynethead

This one is easy, no where in the teaser does it say the engines are running. No tow vehicle, no engine thrust no take off. If the conveyor end came up the plane would fall off the end onto the ground.


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## Fire44

What if the plane tried to land on the coveyor belt runway.....would it stop?????




















































Gary


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## Moosegut

PDX_Doug said:


> In other words, the belt can only move if the plane is moving, and the plane can not move if the belt is moving.[snapback]65965[/snapback]​


Gee, I always hate when I have to disagree with Doug.









Not so my PDX_Friend. Say the plane is traveling forward at 100 MPH. The wheels are turning at 100 MPH (letâ€™s not get caught up in the ratios and such â€" just give me the freedom for the example will ya?







) â€" the belt is moving at 100 MPH also because it exactly matches the speed of the wheels. It does not matter that the belt is moving in the opposite direction of the wheels. That does not mean the plane cannot be moving forward.

The belt moves in direct correlation to the movement of the wheels, but that does not mean the plane cannot be moving forward. So, we do not have circular reasoning here. What we have is a non sequitur, because it cannot follow that the belt will move at the same rate as the wheels while the plane is moving forward. â€œThe conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.â€

So as the plane moves forward, the wheels turn. When the wheels turn, the belt moves at the same speed. With the forward movement of the plane and the rotation of the wheels combined with the reverse direction of the belt, the wheels would actually stop while the plane continued forward. But then the plane would be caught up short and the nose would dive into the belt while the prop chewed it all up and . . . AHHHHHHHH!









Faggeddaboudit.


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## Moosegut

nascarcamper said:


> All I know is when I walk on my treadmill I don't get a breeze in the face.
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> [snapback]65973[/snapback]​


Ya mean . . you don't have DW fanning you as you walk?


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## Moosegut

Now, all of this made me hungry. I'm taking a walk over to the cafeteria. It's Sloppy Joes and Tater Tots today - my fav.


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## PDX_Doug

Moosegut said:


> So as the plane moves forward, the wheels turn. When the wheels turn, the belt moves at the same speed. With the forward movement of the plane and the rotation of the wheels combined with the reverse direction of the belt, the wheels would actually stop while the plane continued forward. But then the plane would be caught up short and the nose would dive into the belt while the prop chewed it all up and . . . AHHHHHHHH!


Moosegut, glad to see you finally get it!









The plane moves forward... Air rushes over the wings... the plane lifts off!

It's just those pesky freewheeling wheels that causes all the confusion!
Whew! Glad to see we finally got THAT one settled!









Happy Flying,
Doug


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## huntr70

GlenninTexas said:


> If you are carrying 1000 lbs of canaries in your Outback and they all simultaniously take off and fly, does it lower the weight you are towing?
> [snapback]65964[/snapback]​


Hmmmmm...

On the same note, If I would seal all the windows and doors, hatches and vents, and then fill the interior of the OB with helium, would I be able to tow a much larger trailer, because now my hitch weight and trailer weight are much lighter.....






























shy

Please don't answer this!!!! I really don't want to know!!!!









Steve


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## nascarcamper

Moosegut said:


> nascarcamper said:
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> All I know is when I walk on my treadmill I don't get a breeze in the face.
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> [snapback]65973[/snapback]​
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> Ya mean . . you don't have DW fanning you as you walk?
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> [snapback]65980[/snapback]​
Click to expand...

She's too busy with the cattle prod keeping me moving.


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## Paul_in_Ohio

Take off the wheels, replace with floats, grab you rod and real, take off and fly to some secluded lake and fish the brain teaser away...










By the way, everyones posts depends on the wheels rolling on the treadmill. The application of forces to attempt the forward motion of the plane will attempt to rotate the wheels, which will be countered by the force of the treadmill which is also attempting to rotate the wheels, in the same direction I might add, and thus attempting to hold the wheels from moving down to the end of the treadmill, and while the wheels are attached to the plane, it attempts to restrain the plane from moving. This then has the forces in balance.

Start the wheels to skid and everything changes... Disconnecting the wheels from the treadmill uncouples the forces as the treadmill is only matching the rotation of the tires. The extra force from the unit of propulsion is now able to move the airfoils through the air and will eventually, given enough power, gain enough airspeed to allow lift to overcome weight, and you can become airborn.


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## Moosegut

Paul_in_Ohio said:


> Take off the wheels, replace with floats, grab you rod and real, take off and fly to some secluded lake and fish the brain teaser away...
> [snapback]66021[/snapback]​


Now, that's the first answer that makes ANY sense.


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## Morrowmd

How about this-

Take a model airplane to the grocery store (when its not to busy), put it on the conveyor belt and have the check out girl match the speed of the wheels as you push the model airplane.

If I walk down the checkout aisle with my hand behind that model airplane, it is going to move forward no matter how fast the conveyor belt is moving.

Same logic with the full size jet.


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## PDX_Doug

Excellent example Morrowmd!









Ignoring rolling resistance and friction - as we have throughout this discussion, the belt could be moving 1,000MPH (in either direction!), and without any other outside force acting on the aircraft, it would sit stationary in one spot (think of the magician pulling the tablecloth out from under a full wine glass without moving or upsetting it).

Add the thrust provided by the engine(s), and the plane will move forward, and ultimately lift off. Again, it is the freewheeling wheels that permit this, and that is a vastly different situation than you would have with, say, an automobile - with driven wheels - on that same moving runway (An example that I think is easier to grasp).

OK, I'll shut up now!









Happy Trails,
Doug


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## skills4lou

OK, now think about this: Let's say you're towing your Outback down the road at 65mph. Your wheels are going anywhere from zero mph to 130mph. Going back to the relative motion post: the top of you're wheels are going 130 mph in direction of travel, and the bottom is going zero. Chew on that one for a while :B!


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## Thor

I hate to disagree with you PDX

The plane will not take off because there is no forward motion to create lift. It does not matter if the wheels are powered or not. The rule is that the conveyor speed matches the tire rotation speed. Since the speeds are in opposite directions are the same there is no relative motion. The wheels are attached to the plane hence no motion. Since the conveyor belt is not physically moving, there is no motion. The only way for the plane to move forward is that the tires have to spin faster than the conveyor regardless of what causes this and since the conveyor matches the tires rotation, there will never be forward motion.

Maybe a better way to explain my point would be this.

If you are in a sail boat with no wind and you hold a fan pointing into the sails, there would not be any motion. The force of the fan is equal to the force of holding the fan. The force of you holding the fan is the same force holding in the boat. Since the sails are attached to the boat and you are on the boat, there will be no motion because all forces are equal. Now move the fan to shore and point it into the sails the boat will move forward because there is no opposing force on the boat.

PS - for some reason I am really enjoying this thread









Thor


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## CamperAndy

Thor said:


> I hate to disagree with you PDX
> 
> The plane will not take off because there is no forward motion to create lift. It does not matter if the wheels are powered or not. The rule is that the conveyor speed matches the tire rotation speed. Since the speeds are in opposite directions are the same there is no relative motion. The wheels are attached to the plane hence no motion. Since the conveyor belt is not physically moving, there is no motion. The only way for the plane to move forward is that the tires have to spin faster than the conveyor regardless of what causes this and since the conveyor matches the tires rotation, there will never be forward motion.
> 
> Thor
> [snapback]66083[/snapback]​


I said it before and Doug has said it and a couple of others have said it. It does not matter what the conveyor belt does. People seem to be confused as to which way the belt is moving so let me give both examples.

Everyone must accept that the engines are causing (or trying to cause) the plane to be pushed forward since they act on the air not the wheels.

Since there is forward rotational force on the tires and say the belt attempts to match the forward rolling of the tires by moving forward also. The tires do not roll but the plane picks up air speed and will lift off.

Say the belt is going the other way at the same speed as the forward rotation of the tires. The plane still moves forward but will use twice the amount of runway since the runway and plane are moving in opposite directions at the same speed.

And as Forest Gump would say. Thats all I have to say about that.


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## mswalt

I say, take a car. And while you're at it, pull the Outback, too.

Mark


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## PDX_Doug

Heavy sigh...


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## tdvffjohn

If you are on a down escalater and you are walking in the up direction and the escalator is going at the same speed as your pace, will you ever reach the bottom?


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## BoaterDan

Yes of course it would take off. The forward motion (and resulting airflow over the wings) is caused by the thrust of the engine against the atmosphere, not against the belt.

For those of you that think it wouldn't, the logic you've used would require that if the plane had no engine going at all, and the belt started moving but there were motors in the plane's wheels to turn them opposite to the belt at the same speed then the plane WOULD take off - and of course that's patently absurd.

The plan would of course stay perfectly still in that case, demonstrating that the synchronization of the belt to the wheels is completely independent of the movement of the plane resulting from the engine's thrust.


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## Morrowmd

OK, one last try here.

Suppose everything is the same but the plane has a cable connected to the nose. The other end is connected to a winch at the end of the runway.

When that winch is turned on and starts pulling in the cable the plane will start to move forward no matter how fast the conveyor belt moves. The wheels are free wheeling and independant from the movement of the plane.

There is no way if that cable is getting shorter that the plane won't get closer to the end of the runway. The winch will reel the plane in.

This is the same concept as the jet engine being attached!


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## Paul_in_Ohio

Check this out...

(It's a little bit down the page)

http://www.avweb.com./news/columns/191034-1.html

Paul


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## PDX_Doug

*BRAVO PAUL!!!*









You are da man!









I couldn't have said it better myself! BTW, good to see another AVweb reader in the group.







Obviously, I have gotten a little behind in my reading (probably due to all the time I have spent arguing this issue!)

Happy Trails,
Doug


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## Thor

Good find on that web site. However, I will throw this part into the equation. The web site show a prop plane. Of coarse this would creat lift. Even if you prevent forward motion completely the prop will force air over the wings creating lift. The Plane does not have to move because you are moving the air over the wings. Imagine a rope tie to the back of the plane anchored to the ground..the plane will still lift given enough airspeed for the wings even without forward motion. Like a kite. If it was a jet would it still hold true. A fighter plane throttles up while the brakes are on...there is no lift created until the fighter plane moves forward. There is no force creating relative airspeed to the wing. The sling shot increases the forward motion of the plane hence increase lift

The winch example - If a winch pulls the plane forward on the conveyor belt, yes this would create lift because ther is forward motion creating airspeed. Again, the problem stats that the wheels spin at the same rate as the conveyor. So a winch would pull the plane forward but the wheel speed would have to be faster than the conveyor belt to have relative forward motion.

Lift is created by airspeed or the air moving over the wing. This can be created by moving the wing through the air or by moving the air over the wing. If there is no relative motion between wing and no lift. The prop plane creates lift by moving air over the wing. A jet creates lift by moving the plane through the air.

I agree that the speed of the conveyor does really matter in the prop example and the plane will lift however;

Lets take a car on the conveyor - I think everyone would agree that if you are standing on the ground beside the car on the conveyor there would be no motion forward. If you were driving the car and stuck your hand out the window there would be no breeze because the car is not moving forward. (Not if you are in a prop plane and did this there would be a breeze because of the prop)

Now put a jet engine on car and put it in neutral. Again the car would not move forward because the wheels have to turn relative to the ground you are standing on, since the conveyor belt is at the exact same speed ther would be no realtive motion. The only way there can be forward motion is if the wheels spin faster than the conveyor which this problem does not allow. No forward motion with no way a moving air over the wing no lift. The web site proves that because the plane did not move forward.

So my long winded answers is:

If the only way to create lift is by the forward motion of the plane, the plane will no lift.

If the you are allowed to move the air relative to the plane (by prop, gust of wind etc) the plane will lift and be stationary relative to the ground.

PDX & everyone - again great discussion - Thanks

I love these type of problems - I need a beer

Thor


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## Steelhead

Here, Here ! great treatise my man
















Dallas


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## 2500Ram

Ok, I've stayed out of this for the last few days now. Yes the plane will fly, jet or prop. Thor, your example of a car in neutral with a jet will go forward very fast, same as the plane. Who cares how fast the wheels are spinning, they are merely holding the car up/plane, the jet doesnâ€™t care about the wheels, the wheels are only spinning in either scenario because there is what... forward movement








Think about thatâ€¦

Bill.


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## sircarryalot

2500Ram said:


> This was posted on a different board and there has been good debate on both sides, it's about a 50 50 split, your opnion...
> 
> Bill.
> 
> *** Brain Teaser ***
> 
> Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.
> There is no wind.
> 
> Can the plane take off?
> [snapback]65896[/snapback]​


Think of it this way, try landing the plane. Is the plane going to stop dead in its tracks when it hits the ground......no. Of course the plane can take off. Or you can think of it this way, Get a bunch of people and tie a rope to the plane, stand at the end of the runway and pull the rope, is the plane moving on the conveyor belt?

Merry Christmas All !!


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## nascarcamper

2500Ram said:


> Ok, I've stayed out of this for the last few days now. Yes the plane will fly, jet or prop. Thor, your example of a car in neutral with a jet will go forward very fast, same as the plane. Who cares how fast the wheels are spinning, they are merely holding the car up/plane, the jet doesnâ€™t care about the wheels, the wheels are only spinning in either scenario because there is what... forward movement
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> Bill.
> [snapback]66162[/snapback]​


I agree with the argument of the thrust however the wheel speed will be proportional to the aircraft speed so I'm still not conviced it will fly if the conveyor keeps up with the wheel speed in the opposite direction. That's my story and I'm sticking to it.


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## 2500Ram

Ok, last try.

The plane is stopped, not moving. Engine is on and giving thrust now. The "plane" wants to move forward lets say 10mph the conveyer belt then has to move at lets say 20mph the opposite direction to compensate the wheels spinning. Still with it?

Next more thrust is given and now the "plane" is moving at lets say 50 mph but the "wheels" are moving at lets say 100mph to compensate for the speed of the treadmill. Still there. The wheels are moving faster then the plane but the plane is moving forward.

sunny



> Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.
> There is no wind.
> 
> Can the plane take off?


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## PDX_Doug

I can't believe we are still arguing this!









OK Thor, let me clear up a couple of misconceptions here...



Thor said:


> The prop plane creates lift by moving air over the wing. A jet creates lift by moving the plane through the air.


Um, how should I put this... oh yeah, WRONG! (I'm sorry, that was uncalled for!)
Any airplane (jet, prop, rocket, what-have-you) creates lift by moving an airfoil through the air. The prop on a propeller driven aircraft however provides a negligable (read: almost too small to measure) amount of air flow over the wing as far as lift is concerned. The props sole purpose is exactly the same as the jet engine, that is to say, provide forward thrust. As far as the airplane in the photo is concerned, notice that the prop is not moving air over the wings nearly as much as it is over, under and around the fuselage. If the props purpose was to create lift, it would be located elsewhere. And what about 'pusher' configuration airplanes, where the prop is located in the rear of the plane? The prop is located in the front of most airplanes because it is easier, a jet engine is located aft or behind the wings so the exhaust doesn't melt the airplane and turn the occupants into Hot Pockets!



Thor said:


> Lets take a car on the conveyor


Actually, let's not. The differences in dynamics between a thrust driven vehicle, with free turning wheels (airplane) and a vehicle driven by a mecahnical connection between the vehicle and mother Earth (the tires of a car), is like night and day. This difference is the whole reason this discussion presists. In general, we are much more familier with the physics of the automobile, and naturally try to apply these principals to this situation. The problem is, they just do not apply. It's the classic apples and oranges thing!

So there!

Happy Trails,
Doug


----------



## Katrina

If the same plane is sitting out on a frozen ice covered pond and has his brakes applied to the wheels, could he take off?
Why yes, just like he could on the conveyer.
Just had a real good argument with DW about this.


----------



## johnp

Now for the real questions

The plane tires are they P-rated or LT-rated

What is the CGVW

What type of hitch and sway will be needed

Ford Chevy Dodge Nissan or Toyota

Gas or Diesel

Sorry I had to









And yes the plane will fly

John


----------



## nascarcamper

2500Ram said:


> Ok, last try.
> 
> The plane is stopped, not moving. Engine is on and giving thrust now. The "plane" wants to move forward lets say 10mph the conveyer belt then has to move at lets say 20mph the opposite direction to compensate the wheels spinning. Still with it?
> 
> Next more thrust is given and now the "plane" is moving at lets say 50 mph but the "wheels" are moving at lets say 100mph to compensate for the speed of the treadmill. Still there. The wheels are moving faster then the plane but the plane is moving forward.
> 
> sunny
> 
> 
> 
> 
> Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.
> There is no wind.
> 
> Can the plane take off?
> 
> 
> 
> [snapback]66176[/snapback]​
Click to expand...

match the speed of the wheels I see said the blind man. shy


----------



## PDX_Doug

nascarcamper said:


> match the speed of the wheels I see said the blind man. shy


Let's see... That's one down, Thor to go!

Sorry









Happy Trails,
Doug


----------



## 2500Ram

PDX_Doug said:


> Let's see... That's one down, Thor to go!
> 
> Sorry
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Happy Trails,
> Doug
> [snapback]66194[/snapback]​

















Thor read above









This has been fun though.

Bill.


----------



## Thor

Love it - Still not convinced, however nice try.

The ice thing - cannot be used because there is relative motion between the plane and the ground. The purpose of the conveyor is to prevent relative motion.

PDX

The prop plane. Yes the prop provides forward thrust but also pushes air over and under the wing creating lift. A staionary plane with a wind blowing against the wing will create lift. A normal plane takes off against the wind to increase the relative speed between the wing and the air moving around it. A plane flying at 100mph against a head wind of 100mph will create the same amount of lift as a plane flying at 200mph with no wind. If a plane is travelling at 100mph and the is blowing at 100mph in the same direction there is no relative speed between the wing and the air, hence no lift is created. Do you agree?

Point #1 - Lift is created by relative speed between the wing and the air moving around it. (this is true reglardless of what force causes this..wind, fan, forward motion,etc)

The car thing has to be considered. I toured the Harley plant and part of there quality control is to run the bike on a set of rollers to 70mph (relative to the rollers but 0mph to the ground) The bike rear wheel speed is also match by the rollers to ensure the bike does not move. You have to agree with this one as well? Now put wings on the bike...the bike will not fly because there is no relative motion between the air; but the bike speedo is reading 70mph. The bike is held in place by the rollers rotating in the opposite direction at 70mph.

I know what you are going say - the wheel of the bike is powered hence the difference and the example is not valid. Don't go there yet.

The jet is different than a prop plane. While on the run away stationary a prop plane throttles up ready to take off but the brakes are on so the plane is not moving forward. There is lift created because the prop is acting like a fan moving air around the wing. A Fighter jet in the same situation will only create lift as the plane is moving forward because there is no air movement around the wing. Do you agree with the above?

The wheels and the plane are physically attached to each other so they act as one. If the plane is moving forward the wheels are moving forward regardless what force creates the forward motion. Now the tires are able to rotate which is different than moving forward (the bike on the rollers)

Point #2 - Even the other web site shows that the plane does not move relative to the ground because the rotatation of the conveyor is match by the rotation of the wheels. (same as the bike on the rollers) You also have to agree with this one.

So the only way to create lift is to have the air movement around the wing. Since the plane is at 0mph relative to the ground and the air is at 0mph to the ground (no wind) what creates the lift? In the web example it is the prop pushing the air around the wing. No prop no lift.

Now one last thing The conveyor does not know what causes the tires to rotate, all it knows is to match the speed. So it does not matter if the wheels are powered or not if the tire rotates the conveyor rotates. The web site proves at as well because the plane reamins stationary realtive to the ground.

So there









Thor

I know we will not agree on this so does anyone know someone at a University that teaches physics?


----------



## nascarcamper

Thor said:


> Love it - Still not convinced, however nice try.
> 
> The ice thing - cannot be used because there is relative motion between the plane and the ground. The purpose of the conveyor is to prevent relative motion.
> 
> PDX
> 
> The prop plane. Yes the prop provides forward thrust but also pushes air over and under the wing creating lift. A staionary plane with a wind blowing against the wing will create lift. A normal plane takes off against the wind to increase the relative speed between the wing and the air moving around it. A plane flying at 100mph against a head wind of 100mph will create the same amount of lift as a plane flying at 200mph with no wind. If a plane is travelling at 100mph and the is blowing at 100mph in the same direction there is no relative speed between the wing and the air, hence no lift is created. Do you agree?
> 
> Point #1 - Lift is created by relative speed between the wing and the air moving around it. (this is true reglardless of what force causes this..wind, fan, forward motion,etc)
> 
> The car thing has to be considered. I toured the Harley plant and part of there quality control is to run the bike on a set of rollers to 70mph (relative to the rollers but 0mph to the ground) The bike rear wheel speed is also match by the rollers to ensure the bike does not move. You have to agree with this one as well? Now put wings on the bike...the bike will not fly because there is no relative motion between the air; but the bike speedo is reading 70mph. The bike is held in place by the rollers rotating in the opposite direction at 70mph.
> 
> I know what you are going say - the wheel of the bike is powered hence the difference and the example is not valid. Don't go there yet.
> 
> The jet is different than a prop plane. While on the run away stationary a prop plane throttles up ready to take off but the brakes are on so the plane is not moving forward. There is lift created because the prop is acting like a fan moving air around the wing. A Fighter jet in the same situation will only create lift as the plane is moving forward because there is no air movement around the wing. Do you agree with the above?
> 
> The wheels and the plane are physically attached to each other so they act as one. If the plane is moving forward the wheels are moving forward regardless what force creates the forward motion. Now the tires are able to rotate which is different than moving forward (the bike on the rollers)
> 
> Point #2 - Even the other web site shows that the plane does not move relative to the ground because the rotatation of the conveyor is match by the rotation of the wheels. (same as the bike on the rollers) You also have to agree with this one.
> 
> So the only way to create lift is to have the air movement around the wing. Since the plane is at 0mph relative to the ground and the air is at 0mph to the ground (no wind) what creates the lift? In the web example it is the prop pushing the air around the wing. No prop no lift.
> 
> Now one last thing The conveyor does not know what causes the tires to rotate, all it knows is to match the speed. So it does not matter if the wheels are powered or not if the tire rotates the conveyor rotates. The web site proves at as well because the plane reamins stationary realtive to the ground.
> 
> So there
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Thor
> 
> I know we will not agree on this so does anyone know someone at a University that teaches physics?
> [snapback]66210[/snapback]​


I took it that the twist is wheel speed is not ground speed and that's what confused the (insert bad word here) out of me. The article didn't convince me until I got 2500ram's post with the red text.


----------



## CamperAndy

And a Bumble Bee can't fly either.


----------



## huntr70

So, I'm thinking that since the airplane, jet, whatever, is using the air as the propellant, it should move and take off irrelevant of the conveyor belt.

It would be like shooting a Matchbox car with a rubber band like a slingshot on a treadmill...the belt is moving, the wheels are spinning, but the car will still go forward because it is not using the wheels as a propulsion system.

Which came first...

the chicken or the egg???

Who's on first???

I AM SOOOO CONFUSED..........









Steve


----------



## Paul_in_Ohio

Is the plane African or Europian????


----------



## Katrina

Paul_in_Ohio said:


> Check this out...
> 
> (It's a little bit down the page)
> 
> http://www.avweb.com./news/columns/191034-1.html
> 
> Paul
> 
> 
> 
> 
> 
> 
> 
> 
> [snapback]66135[/snapback]​


Katrina here. I usually don't post on the boards, Jim does it all the time, but this caused us to debate all night and again this morning. So I'm feeling the need to drop my two cents worth.

The question poses that the conveyor belt matches exactly the speed of the wheels. The above website states "A few moments later, the roaring Continental, spinning that wooden Sensenich prop, has accelerated the J-3 and Manfred to 25 mph indicated airspeed. He and the airplane are cruising past the cheering spectators at 25 mph, while the conveyor has accelerated to 25 mph eastbound, yet it still has no way of stopping the airplane's movement through the air. The wheels are spinning at 50 mph, so the noise level is a little high, but otherwise, the J-3 is making a normal, calm-wind takeoff."

Reading this I see that the conveyor is moving at 25 mph while the wheels are moving at 50 mph. That is not matching the exact speed of the wheels therefore allowing forward movement. In my mind, if the numbers were exactly matched, there would be no forward movement and therefore no airspeed to allow for takeoff. (given there is also no wind movement)

I also found this explanation at another site. "The plane would rise if the air on its lifting surfaces was moving across them faster than the plane's stall speed. Aircraft carriers head into the wind so that the speed over ground is lessened, relative to the speed of the (moving) ship. If the plane must go 140 kts relative to the air it is flying through, and there is no wind, it will only need to go 120 kts relative to the deck of a carrier going 20 kts in the same direction as the takeoff. Into a headwind of 20 kts, in that scenario, the plane will have sufficient life to take off at what would appear to be 100kts to someone standing on that same carrier. Speed through the air is what counts. A plane could be on a conveyor going 1000 kts and keeping that pace, but if the air over the control and lift surfaces (wings) does not move, the plane will not go up."

I have posed this question to an aerodynamics engineer and will let you know the answer I receive.

Meanwhile, I agree with Thor.


----------



## Morrowmd

The conveyor belt is matching the speed of the wheels, not the speed of the plane! I like this explantion:



> Think of it this way, try landing the plane. Is the plane going to stop dead in its tracks when it hits the ground......no. Of course the plane can take off.


If the plane were landing and the conveyor matched the speed of the wheels at the instant it touched down, would the plane instantly stop!

If so lets call the Navy, we have invented an aircraft carrier that is only 50' long!

You've got to keep in mind that the wheels and conveyor belt have nothing to do with the movement of the plane.

I love brain teasers














, keeps the mind working.


----------



## Guest

OK, I feel compelled to stick my nose into this. I spent over 25 years flying, even a dummy like me has to pick up something.

Point one: The wheel bearings in the landing gear negates all but a very small (friction) part of the effect of ground speed over airspeed. The plane flies by airspeed. No thrust is being applied to the wheels, they only spin because of friction between them and the ground/conveyor belt.

Point two: If the conveyor belt moves in oposite but equal relationship to the speed of the tires across it, the the belt will not move. Unless the tires are skidding, there is no movement of the portion of tires that is in contact with the ground in relationship to the ground/conveyor belt.

This concludes this transmission, you will now be returned to you're regularly scheduled program.









Happy Camping,
Gary


----------



## mswalt

, what color is the plane?

Is it right-winged or left-winged?

What side is the door on?

Just how big is that darn conveyor belt?

Mark


----------



## PDX_Doug

OK, let's try this on for size...

Let's apply the logic that Thor and others have used, but make one 'little' - but as it turns out, very significant - adjustment to what has been presented.

We have all been visualizing the plane plane trying to move forward, and the 'runway' belt moving backwards to counter the movement of the wheels, thus stopping the wheels and the plane. Sounds reasonable, right? The only problem is, in order for the runway to counter the rotation of the wheels, it too has to move forward as well!

As a way of explanation, let me paint a little picture here. Let's say you are standing beside the runway. The plane is off to your left, and attempting to move forward down the runway from your left to your right to take off. Now think about what the wheels would be doing... As the plane moves from your left to your right, the tires will want to roll in a clockwise direction. Any given point on the tire will roll under from the front of the plane (right), cross the tarmac, and reappear towards the rear of the plane (left). With me so far? Good.

Now let's visualize what the belt will have to do to stop that rotation. The belt would have to move forward (from our left to our right) - with the aircraft as well - in order to apply a counter-clockwise force to the wheels, and stop them from rotating.

So now it is easy to imagine the aircraft moving forward on a runway that is moving along with it. As the plane picks up speed, the runway belt does the same - keeping pace - and we can visualize the plane moving along from our left to our right, the runway moving along with it, all the while, the wheels of the plane remain motionless (relative to the runway). The plane is moving forward, the runway is moving forward, the wheels are not turning... everything fits the equation, right?

Now let's add the element of the air around the plane to the mix. The air is in no way 'attached' to the runway, and in fact is motionless to us observers standing beside the runway. The airplane (along with the runway) however is moving through the air in a forward (left to right) direction. Once the speed of the aircraft/runway combo achieves the needed velocity, enough lift will be generated over the wings and the plane will soar into the heavens!

Using this approach, all the restrictions of the original question have been satisfied, and the plane is able to take-off.









Happy Soaring,
Doug

Additional thought added after the fact:
If you are still having a tough time seeing this, instead of a moving runway, imagine the plane is sitting on a cart, or dolly., which itself is moving down a normal runway. The plane will easily move the dolly along with it as it progresses down the runway. The wheels on the dolly will be turning, but the wheels on the plane will be stationary as the 'ground' (dolly) they are resting on is moving with them, so there is no relative motion between the two. Now, just substitute the moving belt for the dolly, and you have exactly the same situation.


----------



## GlenninTexas

Guys, I posed the question to some of my team and one of then went to a physics professor at University of Texas. Here's his response. There are actually two emails here.

Folks,

Here is the physics answer. The phrase " match the speed of the wheels 
in the opposite 
direction of rotation" is not unique since the wheel rotates but the 
belt moves linearly. To make it unique we must assume that the 
motion of the wheel relative to the belt is specified at the point of 
contact. Then for rotation in the SAME direction as the converyor belt 
the plane does not fly for the reasons Mike gave, but the phrase "match 
the speed in the OPPOSITE direction of rotation" would give the plane twice the 
velocity to that with no conveyor belt. Thus, the plane takes off.

I see this by drawing pictures of the wheels rotating on the conveyor belt 
with speed Vconv = 0 then with speed Vconv= omega*R and Vconv =-omega*R 
where omega is the angular speed of the wheel and R is its radius. One is 
assuming that there is not slippage of the tire on the belt.

Of course, I would probably have given Mike's answer if I had not analyzed 
his answer and the then drawn these pictures to look for a contradiction.

Wendell

> Hello Wendell,
> 
> The guys are talking about this one - Glenn says it will take off. Maybe a trick question ???? anyway they are wondering about the answer from a physics professor!
> 
The plane will take off due to the fact that the engines are providing the thrust and not the wheels.
> 
> I do not understand how the plane could take off with two equal and opposing forces. 
> I know that I must be missing a fundamental principle for example that air provides resistance but I have not been able to connect the dots yet.
> 
> I know that if a float plane tries to take off from a river that it will be unable to if the airplane is unable to counteract the river's current.


----------



## cookie9933

Well, Ram2500 mentioned thathe was confused when he started this thread. Now with Wendell's physics explanation, all confusion is dispelled. Glad we got to the bottom of that one, huh?

Bill


----------



## BoaterDan

So, everyone now has seen the light and agrees the plane will take off, right?


----------



## Fire44

I vote that we all get off the plane and go into the airport bar. We can sit and watch it try to take off!!!!!

I have a headache now.......

Gary


----------



## BoaterDan

Fire44 said:


> I vote that we all get off the plane and go into the airport bar. We can sit and watch it try to take off!!!!!
> 
> I have a headache now.......
> 
> Gary
> [snapback]66282[/snapback]​


And watch the belt rip to shreds and the bearings on the pulleys burn out as it tries to run at the 200 mph!









Wait, am I describing an imaginary scene or watching Lions football?


----------



## Thor

GlenninTexas said:


> Guys, I posed the question to some of my team and one of then went to a physics professor at University of Texas. Here's his response. There are actually two emails here.
> 
> Folks,
> 
> Here is the physics answer. The phrase " match the speed of the wheels
> in the opposite
> direction of rotation" is not unique since the wheel rotates but the
> belt moves linearly. To make it unique we must assume that the
> motion of the wheel relative to the belt is specified at the point of
> contact. Then for rotation in the SAME direction as the converyor belt
> the plane does not fly for the reasons Mike gave,


I took it as above.

Now regarding the toy car and the tread mill. The only way it will go up is if the tires are faster than the conveyor. It is like walking up a down escalator. You will only go up if you are faster than the escalator. You will reamin in the same spot if the speeds are equal and you move down if you are slower.

Awesome group discussion







Alot of great points without anyone getting mad. That is why I like Outbackers.com so much. Different opinions respected by all.

Thanks again,

Thor


----------



## huntr70

Thor said:


> [Now regarding the toy car and the tread mill. The only way it will go up is if the tires are faster than the conveyor. It is like walking up a down escalator. You will only go up if you are faster than the escalator. You will reamin in the same spot if the speeds are equal and you move down if you are slower.
> 
> [snapback]66388[/snapback]​


You've got the start of it...now take the drive out of the wheels on the toy car, and add a propulsion system. (slingshot it)....then it does not matter how fast the wheels go, as they are not the driven system anymore.

Steve


----------



## BoaterDan

Just to expand on Steve's point with a little more illustration.

Imagine you're standing at the bottom of the down escalator. You know that if you step onto the escalator and walk at exactly the same speed as it you will go nowhere.

Now, get back on the floor below the escalator and imagine you have a jetpack on your back. You turn it on and aim it such that it pushes you up the path of the escalator - what happens?

?
?
?
Well, you go up the escalator, of course. Even if you do nothing with your legs. The only way you don't go up the escalator is if you plant your feet on one of the steps and can hold back the force of the jetpack.

But in the plane question there is no such force being applied.

Another scenario... imagine you're standing at the airport on one of those conveyor belts moving towards you and you're on rollerblades with a jetpack. You turn on the jetpack and aim down the conveyor path. Now, what happens? You move of course? Even if the conveyor would normally push you back? Why? Because you're on WHEELS.

In the plane question the wheels are free-wheeling and have a negligible amount of resistance relative to the thrust of the motor by definition. The wheels and their interaction with the conveyor belt is completely irrelevant. It doesn't matter if the conveyor is moving against the wheels at the same speed or with them at twice the speed - the plane moves forward because of the thrust of the engine.


----------



## PDX_Doug

As the debate continues to rage, even spilling over into another thread, I thought maybe a visual would help clarify the situation. Please forgive me for the crudeness of the graphic... shy










Not only does the example shown meet all the requirements of the original question, but can take it a step beyond. Imagine that the belt is not powered to match the wheel speed but freewheeling itself. Also imagine that the pilot has the wheel brakes on. As long as the engine/propeller can produce enough thrust to move the combined masses of the airplane and the belt, the same result will be accomplished. Again, without the wheels ever turning (or even skidding)!

Happy Trails,
Doug


----------



## nascarcamper

PDX_Doug said:


> As the debate continues to rage, even spilling over into another thread, I thought maybe a visual would help clarify the situation. Please forgive me for the crudeness of the graphic... shy
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Not only does the example shown meet all the requirements of the original question, but can take it a step beyond. Imagine that the belt is not powered to match the wheel speed but freewheeling itself. Also imagine that the pilot has the wheel brakes on. As long as the engine/propeller can produce enough thrust to move the combined masses of the airplane and the belt, the same result will be accomplished. Again, without the wheels ever turning (or even skidding)!
> 
> Happy Trails,
> Doug
> [snapback]66504[/snapback]​


Wait a minute now. If the wheels match the conveyor by your diagram neither would be moving so the plane would be sitting still and therefore would not fly???


----------



## PDX_Doug

nascarcamper said:


> Wait a minute now. If the wheels match the conveyor by your diagram neither would be moving so the plane would be sitting still and therefore would not fly???


Wrong! The wheels would be sitting still only in relation to the belt. The belt and the plane would both be moving forward. Because they are both moving forward together (at the same rate), the wheels do not need to turn. As a matter of fact, we don't even need wheels!

Wow, I think I have just invented the aircraft catapult! You know, you could mount something like this on a ship...

Hmm...now what to call it?

Doug


----------



## Thor

PDX

Arhmmmm!!!



> Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.
> There is no wind.


Conveyor exactly matches the speed of the wheels moving in the opposite direction. It does not state wheels rotating in the opposite direction. (as your nicely drawn diagram indicates)

I think the intent is the would be motion of the wheels forward or backwards not the rotation of the the wheels.

It is never over until the fat lady sings.









Thor


----------



## nascarcamper

PDX_Doug said:


> nascarcamper said:
> 
> 
> 
> Wait a minute now. If the wheels match the conveyor by your diagram neither would be moving so the plane would be sitting still and therefore would not fly???
> 
> 
> 
> Wrong! The wheels would be sitting still only in relation to the belt. The belt and the plane would both be moving forward. Because they are both moving forward together (at the same rate), the wheels do not need to turn. As a matter of fact, we don't even need wheels!
> 
> Wow, I think I have just invented the aircraft catapult! You know, you could mount something like this on a ship...
> 
> Hmm...now what to call it?
> 
> Doug
> [snapback]66520[/snapback]​
Click to expand...

Wrong! "The conveyer belt is designed to exactly match the speed of the wheels at any given time" With your theory if the wheels don't move the plane don't move. The plane will indeed fly but not by your reasoning.


----------



## PDX_Doug

Thor... nascarcamper...

Please just do me one favor. Don't ever go to work for Boeing!

I understand that AirBus is looking for Engineers though...









And that is all I have to say about that.

Happy Trails,
Doug


----------



## Thor

At least we agree that we both made the right choice buying an Outback. Based on that we all have to be smart people. Conveyor belt or no conveyor belt.

Thor


----------



## Thor

Morrowmd said:


> The conveyor belt is matching the speed of the wheels, not the speed of the plane! I like this explantion:
> 
> 
> 
> 
> Think of it this way, try landing the plane. Is the plane going to stop dead in its tracks when it hits the ground......no.Â Of course the plane can take off.
> 
> 
> 
> If the plane were landing and the conveyor matched the speed of the wheels at the instant it touched down, would the plane instantly stop!
> 
> If so lets call the Navy, we have invented an aircraft carrier that is only 50' long!
> 
> You've got to keep in mind that the wheels and conveyor belt have nothing to do with the movement of the plane.
> 
> I love brain teasers
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> , keeps the mind working.
> [snapback]66246[/snapback]​
Click to expand...

Ok - An aircraft carrier: If the plane did stop instantly, the pilot would continue right thru the front of the jet. Can you imagine the G forces (300mph to 0 instantly) So in order for the pilot to fly again the carrier has to be 51' feet long. But wait if the carrier had a conveyor how would the plane take off






























Thor


----------



## nascarcamper

PDX_Doug said:


> Thor... nascarcamper...
> 
> Please just do me one favor. Don't ever go to work for Boeing!
> 
> I understand that AirBus is looking for Engineers though...
> 
> 
> 
> 
> 
> 
> 
> 
> 
> And that is all I have to say about that.
> 
> Happy Trails,
> Doug
> [snapback]66533[/snapback]​


Getting testy are we? Opinions are like (insert appropriate body part) everyone has one.







And that's all I have to say about that.


----------



## Moosegut

Morrowmd said:


> If the plane were landing and the conveyor matched the speed of the wheels at the instant it touched down, would the plane instantly stop!
> 
> If so lets call the Navy, we have invented an aircraft carrier that is only 50' long![snapback]66246[/snapback]​


Excellent pernt!


----------



## Moosegut

My profound apologies to Doug (I stole your drawing). I have always agreed that the plane would take off, but a previous point you made gave me a visual in my head. Since you posted the drawing, I thought adding your "point" to the drawing might help. The point is: "imagine the plane is sitting on a cart or dolly." The freewheeling wheels and their relationship to the conveyor belt will have nothing to do with its ability to take off. The speed of the conveyor belt is relative to the speed of the WHEELS, not the speed of the PLANE.

If you were to motorize the wheels, and rotate them at 100 MPH in reverse, and then place the plane on a conveyor belt that moves in the opposite direction, the plane would not move because the conveyor belt compensates for the motorized wheels. NOW - Plop that conveyor belt and plane on top of a dolly and start the engines. That plane is moving forward even though the wheels are turning at 100 MPH - IN REVERSE! The plane doesn't care (an anthropomorphism - I know) about the wheels. It's going to move forward because the engine provides the forward thrust irrespective of what the wheels are doing.

A float plane in a river was referenced as an example of why the plane would not take off - that doesn't hold water.







The floats are not freewheeling. Put wheels on instead of floats and the plane does not care what the wheels (floats) are doing in relation to that river. The wheels just spin "freely" faster and the river (conveyor belt) moves faster to compensate for the speed of the wheels, but the plane moves forward.

Scott 
(Again, my apologies to you Doug, for stealing your drawing)


----------



## Thor

Scott

One for the good guys







. Lift is generated by the relative motion of the air around a wing. It does not care where the trust comes from. No relative motion no lift.

Ok, I think I'm done -

Thor


----------



## huntr70

Ya know, I really hate to mention the fact that the drawing is not correct.

The initial statement says "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation."

That is OPPOSITE DIRECTION OF ROTATION.

According to the drawing, the conveyor belt and the wheels are moving the SAME direction of rotation.

Not that it really matters in whether the plane takes off or not, because the initial question also sayed the belt was as wide and long as a runway....not the length of the aircraft. That means if a plane is generating AIR SPEED,not land speed, it will take off.

Take the jet powered drag cars.....they are free wheeling. They do not drive with the wheels. Now, who is going to say that they won't move at all on a conveyor belt when the engine is generating 1000 lbs of thrust....not going to the wheels. Same principle on the plane...except it has wings and will therefore take off.

Steve


----------



## Moosegut

huntr70 said:


> Ya know, I really hate to mention the fact that the drawing is not correct.
> [snapback]66570[/snapback]​


Steve,

I was tempted to change the direciton of Doug's arrow that indicates the direction of the conveyor belt, but I didn't want to take that liberty. I'm sure it was just a drawing error on Doug's part - right Doug? I was also tempted to point out that Doug's wing is upside down. That shape won't fly - sorry Doug, but the longer surface (curved) has to be on top to create the lift. But I'm sure that was just an error also on a quickly put together drawing.

Fly the Friendly Skies,
Scott


----------



## 2500Ram

Moosegut said:


> huntr70 said:
> 
> 
> 
> Ya know, I really hate to mention the fact that the drawing is not correct.
> [snapback]66570[/snapback]​
> 
> 
> 
> Steve,
> 
> I was tempted to change the direciton of Doug's arrow that indicates the direction of the conveyor belt, but I didn't want to take that liberty. I'm sure it was just a drawing error on Doug's part - right Doug? I was slao tempted to point out that Doug's wind is upside down. That shape won't fly - sorry Doug, but the longer surface (curved) has to be on top to create the lift. But I'm sure that was just an error also on a quickly put together drawing.
> 
> Fly the Friendly Skies,
> Scott
> [snapback]66577[/snapback]​
Click to expand...

The conveyor belt is moving in the correct direction. Remeber to counter the speed of the wheels, now take that one step further, the wheels are not spinning anylonger, they are stationary but the plane is moving faster and faster down the conveyer belt. Reread the christmas light post, there is a part 2 in there now. Cross thread contimanation I know.

Bill.


----------



## PDX_Doug

Moosegut said:


> I was tempted to change the direciton of Doug's arrow that indicates the direction of the conveyor belt, but I didn't want to take that liberty. I'm sure it was just a drawing error on Doug's part - right Doug?


Sorry Scott,

but the direction of the belt in the drawing is correct. In fact, it is the whole basis of the argument. I know it seems counter-intuitive, and looks like the wheel rotation and belt direction are the same, but look closer. Pick any point on the wheel and follow it around in the direction of rotation shown (which also is correct for a vehicle moving forward), you will see that point on the wheel - when on the bottom - is not moving forward, but in fact is going backwards. It isn't until the wheel rotates the point around to what would be the nine o'clock position on the drawing that the wheel starts to move forward again.

Now, if you can visualize that, then it should be obvious that the opposite direction of travel for the belt, is to be moving forward. The surface of the wheel is rotating backwards at the point of contact... Forwards is the opposite of backwards... equals: the top of the belt is moving in a forward direction.

*Here is an experiment you can try* if you have a toy car handy: Set the car (represents the airplane) on a piece of paper (represents the convyor belt). Now, without moving the paper, roll the car forward and notice which way the wheels are rotating. With me so far?

OK, now try again. But this time as you move the car forward, move the piece of paper as well (at the same speed of course). If you move the paper in the opposite direction the car is moving, you will see the wheels actually turn twice as fast. Move the paper in the same direction the car is moving - as the drawing shows - and the rotation of the wheels will stop. The car continues to move forward through the air due to the thrust your hand is providing (represents the propeller), even though the wheels themselves are not turning.

Give it a try, and let me know if I am wrong.









Happy Trails,
Doug


----------



## huntr70

2500Ram said:


> moving in the opposite direction of rotation.
> 
> [snapback]65896[/snapback]​


To me, this original quote means that if the wheel is turning clockwise, the belt would have to move counter-clockwise.

That would achieve the opposite direction of rotation.
To me, the easiest way to achieve this is by looking at a car dyno....the tire runs on the drum. The tire rotates clockwise, the drum rotates counter.

Steve


----------



## PDX_Doug

Steve...

What we seem to have here is a difference in interpretation in the wording of the original question. But in the end, one can interperate the question with regards to the wheels and the belt any way they choose, as ultimately it does not matter. Because the relationship between the wheels and the runway is not a factor.

Let's expand the experiment with the toy car and the piece of paper I suggested in my last post. This time, while pushing the toy car (plane) forward through the air (air) with the thrust of your hand (the propeller or jet), pull the paper (conveyor belt runway) through from either direction, and at any speed you want. Heck, yank it through from the front as fast as you can. Now yank it through from the rear equally quickly. What you will find, is that no matter what you do with the paper*, the toy car will continue to move forward from the thrust of your hand.

You will also note, that no matter how quickly or slowly you pull the paper out from under the car, the hand pressure required to keep at car moving at any given speed remains virtually the same. In fact the only difference in pressure will be due to outside friction losses (bearings, axle drag, rolling resistance, etc.), not because of the primary interaction of the wheels and belt. In fact, if you have a helper, have them pull the paper through while you thrust against the toy car with your eyes closed. Does your hand stop moving forward? Can you even tell which direction they are pulling from?

As we see that the plane can and will move forward through the air, and with little to no increase in power output required to do so, there is no reason the plane cannot accelerate to the required takeoff speed. The plane will fly.

For all of the doubters out there, I encourage you... No, let me rephrase that... I'm begging you!... Try the experiment. I think you will find it quite enlightening. After all, seeing is believing!

Happy Trails,
Doug

* This experiment assumes that the paper is pulled out from directly in front of, or behind the toy car. Yanking the paper out from the side will introduce a crosswind component that may make the driver (pilot) lose control of the vehicle and crash!


----------



## Thor

PDX

I also have to disagree with your very nice drawing vs the question.

In your very nice drawing the wheel is rotating counter clockwise and the conveyor belt is rotating counter clockwise. This is the same direction. In your drawing if the belt is turning counterclockwise and the wheels are turning counter clockwise at 100mph, the relative speed of the wing to the air in 200mph, the plane will fly.

If the wheel is turning counterclockwise and the conveyor is turning clockwise at 100mph, the relative speed of the wing to the air is 0mph, and the plane will not fly. (This is how I read the problem)

For those you believe this is only true if the planes motion came from the wheels, please read on. If a plane is flying and the wheels are not touching anything the wheel speed of rotation does not matter at all. Now in this question describes the physical interation of the wheel to the conveyor which fixes the forces to this point and cannot be overriden. Picture this. You now put your finger behind the car toy on a treadmill which is on an incline. The toy car wheels are rotating counterclockwise and the treadmill is rotating clockwise. The speed of the car is 0 relative to the ground because of the force that you require to hold it their. This is true regardless how fast the wheels are turning. This will only hold true if the rotational speeds are equal and opposite. Now for the car to moves up the treadmill, the wheels have to rotate faster than the treadmill. This is true regardless what causes this (your finger pushing it a sling shot a prop). The frame of reference is taken at the wheels an hence the forward speed of the plane has to vary inorder for the problem to hold true. (the wheels are fixed to the plane) I believe this is what our University Grad Outbacker friend was explaining.

I believe the main reason why this is so much fun is becasue the question is very open to be misleading, that is why they are fun and very short. To fully describe the problem to the smallest detail it would be several pages long and would look like something a lawyer would write. But than how much fun would that be?

Thor

Thor


----------



## Moosegut

PDX_Doug said:


> but the direction of the belt in the drawing is correct. In fact, it is the whole basis of the argument. [snapback]66580[/snapback]​


We agree it will fly, right?









The original problem stated that the "conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation." It does not say the conveyor belt is set up to COUNTER the wheel rotation - it matches the speed. So, with the wheels rolling forward (clockwise), the belt moves backward to MATCH the speed.

I believe the idea was not to stop the wheels in one position, which your direction of the belt does, but to allow the wheels to spin without the plane moving - much like the people will do this morning while trying to navigate up the hill I live on, in the 4 inches of snow that fell last night.









What you have postulated STILL ALLOWS THE PLANE TO FLY. It just moves forward with the wheels in one position. With the belt moving in the other direction, the plane moves forward and the wheels start rotating . . .

Okay, as I'm thinking this through (AGAIN!!!) I realize the belt can't MATCH the speed. In your direction it counters the speed and stops the wheel's rotation - that's NOT matching. In my direction the belt would actually have to STOP to match the speed of rotation. If the wheels were rotating at 5 MPH . . .

Oh, forget it! The plane flies.









I'm going to read the Sunday paper and have my coffee before church.

Scott


----------



## BoaterDan

PDX_Doug said:


> *Here is an experiment you can try* if you have a toy car handy: Set the car (represents the airplane) on a piece of paper (represents the convyor belt). Now, without moving the paper, roll the car forward and notice which way the wheels are rotating. With me so far?
> 
> OK, now try again. But this time as you move the car forward, move the piece of paper as well (at the same speed of course). If you move the paper in the opposite direction the car is moving, you will see the wheels actually turn twice as fast. Move the paper in the same direction the car is moving - as the drawing shows - and the rotation of the wheels will stop. The car continues to move forward through the air due to the thrust your hand is providing (represents the propeller), even though the wheels themselves are not turning.


Thanks Doug. Finally there's an illustration that's about as simple and demonstrative as you can get. Anybody of the, ahem, opinion that the plane won't fly after trying this experiment will never be convinced.

This whole discussion about which way the belt is supposed to be moving is irrelevant. Indeed, that detail is only in the original question for the express purpose of misleading the readers' thinking to concentrate on that detail instead of the obvios truth of the matter.


----------



## Dreamtimers

Thor said:


> PDX
> 
> Picture this. You now put your finger behind the car toy on a treadmill which is on an incline. The toy car wheels are rotating counterclockwise and the treadmill is rotating clockwise. The speed of the car is 0 relative to the ground because of the force that you require to hold it their. This is true regardless how fast the wheels are turning. This will only hold true if the rotational speeds are equal and opposite. Now for the car to moves up the treadmill, the wheels have to rotate faster than the treadmill.
> 
> I believe the main reason why this is so much fun is becasue the question is very open to be misleading, that is why they are fun and very short. To fully describe the problem to the smallest detail it would be several pages long and would look like something a lawyer would write. But than how much fun would that be?
> 
> Thor
> 
> Thor
> [snapback]66601[/snapback]​


I've stayed out of this _until now_.







Had many laughs and more than a few 'wait a minute'







moments. Someone else, and now Thor has suggested using a toy car powered (held) by a hand on a moving belt, (thought the post with the cable for power was right there also). This seems to do what is needed. It takes the frame of reference for movement away from the conveyor/wheels and moves it outside where it should be.

If someone's hand pushes the (freewheeling) toy car along the belt they are moving the car from outside the wheels/belt frame of reference. The wheels and belt can move as fast or slow as they want._(This would be dependent on the exact nature of the belt speed control and I do NOT want to go there)_. The speed of the car's movement to someone standing next to you will be that of the hand pushing the car.

My question for Thor is; if I read the above post correctly. You are holding the car on the belt in a steady position with the wheels and belt turning, (zero ground movement). If you take your hand and move the car along the belt from end to end, it moves with your hand... right?

This movement is from an outside source and is not affected by whatever the wheels are doing. The entire reference to the wheels (in the original post) is part of the illusion to get you to look in the wrong place while the slight of hand happens elsewhere.

The comment about the wheels attached to the plane is also mis-direction. Yes the wheels are attached to the plane for *linear* movement. look at the axel spindle. The question is about the rotational movement of the wheels and the conveyor. If they are freewheeling then *rotationally* they are NOT attached to the plane. If you jack up the tire and spin it, the wheel moves, but the plane does not.

Bottom line IMHO... it flies.

$.02 
PDX for what its worth my read of the original post also gave a CW/CCW rotation to the wheels/conveyor. Think you are bang on elsewhere.

Dreamtimers


----------



## PDX_Doug

Thor said:


> PDX
> 
> I also have to disagree with your very nice drawing vs the question.
> 
> In your very nice drawing the wheel is rotating counter clockwise and the conveyor belt is rotating counter clockwise.


Thor,

Are we looking at the same drawing? Or do clocks move in the opposite direction than mine where you live?









Just try the experiment. Whether it makes sense or not, it works.

Happy Trails,
Doug

P.S.: Thanks for the kind words about the drawing!


----------



## huntr70

Well, at least I agree that the plane will fly......the stupid wheels versus conveyor has absolutely no effect on whether the plane will fly or not............

If God had wanted us to fly he would have given us wings!!!!









Steve


----------



## huntr70

PDX_Doug said:


> Thor said:
> 
> 
> 
> PDX
> 
> I also have to disagree with your very nice drawing vs the question.
> 
> In your very nice drawing the wheel is rotating counter clockwise and the conveyor belt is rotating counter clockwise.
> 
> 
> 
> Thor,
> 
> Are we looking at the same drawing? Or do clocks move in the opposite direction than mine where you live?
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Just try the experiment. Whether it makes sense or not, it works.
> 
> Happy Trails,
> Doug
> 
> P.S.: Thanks for the kind words about the drawing!
> 
> 
> 
> 
> 
> 
> 
> 
> [snapback]66619[/snapback]​
Click to expand...

Actually, they are both moving clockwise.....

unless you look at the plane from the other side..
















Steve


----------



## PDX_Doug

BoaterDan said:


> Thanks Doug. Finally there's an illustration that's about as simple and demonstrative as you can get. Anybody of the, ahem, opinion that the plane won't fly after trying this experiment will never be convinced.


Ahhh... My work here is done!









Thanks Dan!

Happy Trails,
Doug

P.S.: If nothing else, this has done wonders for our post counts, eh Thor?


----------



## wolfwood

Gotta love it







3 days after getting the answer from the Physics Guy and the Oubackers are still debating.... The whole thing makes me dizzy and I must say, I'm glad to have completed all my recent plane trips BEFORE reading this thread. 5 hrs of this on my brain would have been - well - plane







exhausting!

....and you guys saw something odd about the "Lightbulb Debate" on that OTHER site ?????









Glad to be back!


----------



## PDX_Doug

Glad to have you back, Wolfie!

I wondered where you were during all the fun!









Happy Trails,
Doug


----------



## HootBob

Won't take off
Nobody said anything about a pilot being behind the stick























Don


----------



## mswalt

By now, the plane's probably out of fuel anyway!

Mark


----------



## Moosegut

mswalt said:


> By now, the plane's probably out of fuel anyway!
> 
> Mark
> [snapback]66679[/snapback]​
























That was good.


----------



## PDX_Doug

Let's just be happy the question didn't include a helicopter!...









Happy Trails,
Doug


----------



## Thor

Guys

The wheels are attached to the plane. Forward motion of the wheels (not rotational) means the plane moves forward. If the plane is flying and the wheels are not rotating the wheels are still moving forward. The wheels are on the conveyor belt which means that any motion of the plane translates into rotational motion of the wheels.

The plane will fly if the conveyor belt is moving in the same direction as the plane. The plane will not fly if is moving in the opposite direction that the plane wishes to move in. The wheels are rotating to be able to match speeds.

Thor


----------



## Thor

PDX

Sorry, You are right regarding your diagram. I must be posting in early in the morning or late at night.

So In your diagram, the plane will fly. If the conveyor is moving opposite direction to the plane the plane will not fly.

Thor


----------



## PDX_Doug

Thor said:


> PDX
> 
> Sorry, You are right regarding your diagram. I must be posting in early in the morning or late at night.
> 
> So In your diagram, the plane will fly. If the conveyor is moving opposite direction to the plane the plane will not fly.
> 
> Thor
> [snapback]66712[/snapback]​


Thor,

If you would like, I can send you a toy car and a piece of paper?









Or at least a .jpg image of the box it came in. Now, if you could just cover the postage...say, about $900.00*









Happy Trails,
Doug

* Sorry for the cross thread reference, sometimes I just can't stop myself. shy


----------



## OutbackPM

When I buy my new truck I could do with you all to help negotiate. I am sure they would give it to me at no cost just to go away







.

From what I have seen on this particular thread there seems to be confusion as to what the plane is doing on the conveyor belt.

If the belt is infinitely long and the engine off then the plane will eventually be going backwards on the belt driven by the small amount of friction in the wheel bearings. When the engine is turned on the thust path is from the air to the prop or jet to the plane so it will start to slow its reverse direction then move forwrd in the air until it reaches enough speed to fly.

If the engine and belt are turned on at the same time then the friction force resisting rolling in the wheel bearings will be very small compared to the prop or jet thrust now pushing the air so it will go forward immediately and eventually take off. There maybe some ground effect of the conveyor moving backward that would create extra air movement under the wing enabling a shorter take off length (relative to a stationary point, not the belt or the plane).

The point is the wheels if they are doing there job offer very little resitance to rotation in either direction. They are not driven or have thier brakes on so the prop or jet working on the air is the motive force working on the planes movement.

I can see at an Outback rally a camp of "it will" and "it won't" and no one else will have a clue what we are talking about







.

David


----------



## PDX_Doug

David,

I'm glad to see you were able to resist the temptations of the dark side!









Happy Trails,
Doug


----------



## BoaterDan

PDX_Doug said:


> David,
> 
> I'm glad to see you were able to resist the temptations of the dark side!
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Happy Trails,
> Doug
> [snapback]66732[/snapback]​


 sunny Ya know Doug, I think we could come up with some interesting inventions...

A car that accelerates by wind power (in any direction, mind you) as long as the parking break is on.

A smart bomb that accelerates at twice the rate of normal gravitational pull as long as the plane is heading East.

But seriously, reminds me of the teacher I had for the swimming class I took in college as the required PE course. One day we were practicing our survival floating and he said "Ok, everybody go down to the deep end now. It's easier to float in the deep end because there's more water to hold you up." No kidding.


----------



## Thor

PDX

I just re-visited your drawing. (I just had a mirror image of it.

The conveyor is rotating in the same direction as wheels, clockwise. I was my real point.... same direction not opposite. So not to disagree if the orginal question.

If the conveyor belt is moving counterclockwise and the wheels are rotating clockwise, the plane will not move forward and hence it will not fly. In your diagram the conveyor and wheels are rotating in the same direction so the plane will fly. Agree?

Regarding the box...it better have a large X on it.









Thor


----------



## Moosegut

Thor said:


> PDX
> 
> Sorry, You are right regarding your diagram. I must be posting in early in the morning or late at night.
> 
> So In your diagram, the plane will fly. If the conveyor is moving opposite direction to the plane the plane will not fly.
> 
> Thor
> [snapback]66712[/snapback]​


Gee, and here I thought you were in the proper camp Thor.









The physics teacher was back from his honeymoon today.







Guess what? The plane flies no matter what - as long as those wheels are freewheeling. With freewheeling wheels it doesn't matter what that conveyor belt is doing. The forward thrust of the engine moves the plane forward - so long as the wheels are freewheeling. Doesn't matter if the belt moves forward or backward - freewheeling wheels and the plane moves forward and flies.

By the way, did I mention that the plane will fly as long as the wheels are freewheeling?


----------



## wolfwood

ARRRGGGGHHHHH! I just knew I'd find ya'll still here


----------



## OutbackPM

This is close to the answer is'nt it?

We can't let the famous brain teaser disappear yet. But it has been quiet.

http://www.rv.tv/2007/01/28/airplane-lands-on-an-rv/


----------



## 2500Ram

I ain't saying nothing










But there wasn't any conveyor belt under to over powered Winnebago









Bill


----------



## 3LEES

OutbackPM said:


> This is close to the answer is'nt it?
> 
> We can't let the famous brain teaser disappear yet. But it has been quiet.
> 
> http://www.rv.tv/2007/01/28/airplane-lands-on-an-rv/


Dang!

That plane looks just like Doug's drawing!

Go figure.

Dan


----------



## cookie9933

CamperAndy said:


> OK guys the thrust of the jet or prop does not act on the wheels it acts on the air and would cause the plane to move irrespective of the wheel speed.


Absolutely right. The conveyor belt acts on the wheels only. The plane's engines provide thrust acting against the air which moves the plane forward as it would without the conveyor. Result: the plane gets to the speed where (upward) lift overcomes the downward force of gravity and the plane is airborne.

Bill


----------



## PDX_Doug

It warms the heart!









Happy Trails,
Doug


----------



## 3LEES

...waiting for Thor...


----------



## Huskytracks

The Plane will take off. Everything that a plane does is independent of the ground under it. It doesn't matter if the runway is moving backwards at the same speed the plane is moving forward, the wheels will just turn faster and the plane wil go on about its business.
A good illustration of that woiuld be to imagine the runway was covered in ice instead of a giant conveyor. Try to turn the wheels and they would just spin, lock the brakes and the plane would just side towards whatever way is downhill. In that situation a car would be helpless because there would be no traction for the tires and no traction means no control(stop, go, turn). A plane wouldn't even notice the ice. It doesn't care about what's under it. It only cares about the air around it. The engines would thrust the air back, the flight controls would redirect that air to steer, the wings would also use the same air to lift the plane once enough was moving across them. The wheels would just be along for the ride, the plane doesn't care if they spin or not. 
I saw just that happen once up here in alaska. We had a 747 try to take off on a runway covered in ice. The runway was so slick that you wouldn't even be abe to stand up on it. The 747 didn't care, the engines pushed the plane forward just fine and the rudder steered it like nothing was wrong. Everything was good until the pilot panicked and tried to stop. He cut the engines and hit the brakes, air flow stopped and so did all his control. The plane slid right off the side of the runway following the curve of the land. I don't think the wheels even turned during the whole thing.


----------



## wolfwood

PDX_Doug said:


> It warms the heart!
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Happy Trails,
> Doug


It sends chills down the spine!









Some things just won't die will they


----------



## skippershe

wolfwood said:


> It warms the heart!
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Happy Trails,
> Doug


It sends chills down the spine!









Some things just won't die will they















[/quote]
LOL! Here we go again









I missed the first go round, so I'll enjoy watching the reruns


----------



## GlenninTexas

*Again,*

OK, 
Everyone who believes the plane WILL NOT take off line up on the left.

Everyone who thinks the plane WILL take off line up on the right.

People on the left must relinquish their rights to be Outbaker.com members and go join the dark side.
People on th eright may go home and enjoy a beer for being right.

Regards, Glenn


----------



## Lady Di

Glenn,

I guess I'm outa here then because I think it will not take off. If you noticed on the video, the RV is moving in the SAME DIRECTION as the plane. The speed of the wheels alone will not allow the airflow to lift the plane. If the RV had been going in the opposite direction as fast as the plane was going....









That's my theory.


----------



## skippershe

I'll move over to the right because I like it here


----------



## Lady Di

Oh I'm NOT going anywhere.







Neither is the airplane.


----------



## 3LEES

Lady Di said:


> Oh I'm NOT going anywhere.
> 
> 
> 
> 
> 
> 
> 
> Neither is the airplane.


Ahhh...Doug??

Care to 'splain it to Lady Di?? LOL

Dan


----------



## Carey

All I know after reading all 9 pages...................

My head hurts!

Carey


----------



## N7OQ

The plane will takeoff with ease the wheels don't propel the plane down the runway the thrust of the engine does.

If that airplane had 500 2lb birds on board sitting on perch's while the aircraft is flying and all the birds takeoff and start flying around the cargo compartment does the plane get lighter?


----------



## 3LEES

N7OQ said:


> The plane will takeoff with ease the wheels don't propel the plane down the runway the thrust of the engine does.
> 
> If that airplane had 500 2lb birds on board sitting on perch's while the aircraft is flying and all the birds takeoff and start flying around the cargo compartment does the plane get lighter?


HMmmmmmm...

Are the birds flying in formation or in random patterns?









Dan


----------



## Morgueman

If it could take off, we wouldn't need runways. Planes could just be placed on those roller machines used for testing cars (eg. during smog checks). I seriously doubt the plane could take off on this conveyor belt idea.


----------



## BoaterDan

Morgueman said:


> If it could take off, we wouldn't need runways. Planes could just be placed on those roller machines used for testing cars (eg. during smog checks). I seriously doubt the plane could take off on this conveyor belt idea.


OH NO, we've revived the thread from...









I swear I'm only going to make one reply.









The big difference in the car roller machines and a plane is that in the case of a car the spinning rollers are directly counteracting the application of the accelerating force, which is applied via the wheels in the case of a car. In a plane that accelerating force is applied to air, otherwise they wouldn't have props or jet engines. There's no link between the motors and the wheels on a plane - the wheels are freespinning.

A plane rises when there's enough lift generated by air moving over the wings. Period. Nothing else. That's why you can "fly" a plan in a wind tunnel when the plane is not moving forward at all.

Consider this comparison: You put a plane and a car on a freewheeling conveyer, and chain each of them to an object that won't move. When you mash the gas on the car the wheels will start spinning the conveyer. When you mash the gas on the plan all that will happen is you'll have a nice breeze behind it. The wheels and conveyer will not move at all with the plane. Just take this image and turn it around and you have the answer to the puzzler - the wheels and conveyer have nothing to do with the plane taking off or not.

Ok, I'm out.


----------



## Lady Di

Then why have a runway for takeoff? A takeoff pad (conveyor) would then allow all the runways to be used for landing (slowing down) - much more efficient use of space, just get the engine and propeller revs up to speed and the thing should take off. What else should there be? I always thought the runways were to help the plane get to a speed, along with the lift created by the air flowing around the plane, and under the wings, where it had enough airflow under it so it could takeoff.

The air tunnel thing - with enough headwind the plane isn't going anywhere, but it will definitely fly. A little like the conveyor belt. A plane will fly faster with a tail wind, than with a he adwind.

The runways of the future, conveyor belts would free up a lot of space. I'll be really surprised if that idea takes off.


----------



## Doxie-Doglover-Too

CamperAndy said:


> OK guys the thrust of the jet or prop does not act on the wheels it acts on the air and would cause the plane to move irrespective of the wheel speed.


Ha! just as I was reading the first post, I thought to myself" I bet Andy responded to this one!"


----------



## PDX_Doug

Lady Di said:


> Then why have a runway for takeoff? A takeoff pad (conveyor) would then allow all the runways to be used for landing (slowing down) - much more efficient use of space, just get the engine and propeller revs up to speed and the thing should take off.


Again, sorry...

As stated above, the plane flies because of it's speed through the surrounding air. Getting the engine or propeller up to speed provides thrust to move the plane forward, but it is the speed of the air flowing over the wings that creates lift and causes the plane to fly. The runway is necessary because the space is needed to allow the aircraft to accelerate to a speed that produces enough airspeed over the wing to allow takeoff. Sitting stationary on a 'pad' does not create airflow over the wings, no matter how fast the engine/propeller is going. Unless you happen to be in a helicopter!

Happy Trails,
Doug


----------



## bbuchanan2

Ok, I have to chime in on this one myself. What seems to be to be missing in most of these arguments is the effect of gravity and friction upon the aircraft. If the engines are providing thrust (which is defined as a force to provide forward movement) and hence moving the aircraft forward, then the conveyor is providing thrust (force to provide forward movement) in an direction opposite to the thrust generated by the aircraftâ€™s engines. If we assume the conveyor is generating equal amounts of thrust, the aircraft will not move. If we assume the conveyor is providing a lesser amount of thrust than the aircraft engines then there will be forward movement in the direction of the thrust generated by the engines equal to the excess thrust. As long as the aircraft is moving forward at a rate slower than the speed required for the wings to generate enough lift to overcome gravity the aircraft will not fly. Even if the aircraftâ€™s engines are providing twice the thrust the conveyor is providing, the aircraft will likely run out of runway and crash before reaching sufficient speed to overcome gravity. Please donâ€™t forget that until sufficient speed is reached to generate enough lift to overcome gravity, an airplane is basically a very funky shaped car.


----------



## cookie9933

GlenninTexas said:


> *Again,*
> 
> OK,
> Everyone who believes the plane WILL NOT take off line up on the left.
> 
> Everyone who thinks the plane WILL take off line up on the right.
> 
> People on the left must relinquish their rights to be Outbaker.com members and go join the dark side.
> People on th eright may go home and enjoy a beer for being right.
> 
> Regards, Glenn




I just had my beer for being right.

Bill


----------



## tdvffjohn

I m callin Thor







He would not want to miss "part 2"


----------



## 3LEES

The plane in the discussion would fly. I could go on ad nauseam but I would just be repeating lesson's already taught by PDX Doug. Go back in this thread and read his explanations and his illustrations.

I wish the Radio Controlled plane I'm building were finished. I'd be tempted to put this discussion to a real world test.

But then I would do exactly what I'm doing now...drinking my beer of being on the "right" side.









Dan


----------



## lakesider

I guess I'll take the bait and weigh in with my 2 cents:









The answer to whether the plane would fly is probably...

Essentially the engines will exert a force on the surrounding air in a rearward direction. Newton's laws (remember equal and opposite reactions?) apply and thus there would be a forward force on the plane equal to the thrust of the engines. As long as this forward force is greater than all of the rearward forces, the plane would move forward. Doesn't matter what the speed of the conveyor belt is, just what force it would apply to the plane.

If the bearings on the airplane wheels had no friction, the wheels would simply spin at twice the speed they otherwise would have done if taking off from a conventional runway (speed of the plane plus speed of the conveyor). However the bearings would have some frictional force, and part of that frictional force would end up creating a backward force on the airplane. So the acceleration of the plane would be less and it would take a little longer distance to get to takeoff speed. However the frictional force of the wheel bearings would be very small compared to the overall thrust of the airplane engines. Engines are sized with much over capacity in the engines (they can even fly with one engine turned off) so the plane would be able to overcome the rearward force exerted by the wheel bearing friction.

So the plane would move down the runway at almost the same speed as it would have done on a normal runway without a conveyor, it's just that the plane's wheels would be spinning that much faster around. Now is your head spinning too?









A general analogy might be made for a sea plane taking off in a river. Let's say an airplane needs to be travelling at 150 miles per hour to take off. And say the river is flowing at 150 miles per hour from the front of the airplane towards the back. (We won't question the sanity of a pilot with a plane in a river that is flowing 150 miles per hour...







) Assuming the plane is bumped against a rock or something to keep it from flowing backwards (i.e. the plane is not moving at the start) when the engines are rev'ed up they will exert a forward force. As soon as the forward force exceeds the rearward force exerted by the river on the pontoons, the plane will move forward. It doesn't matter what the speed of the river is, just what force it exerts on the plane. As long as there is enough foward force from the engines, the plane will accelerate to 150 mph relative to the air (and 300 mph compared to the river) and will take off. I am neglecting air friction in this which would also exert a rearward drag on the airplane. But again the presumption is the plane's engine(s) are plenty big enough to overcome that.

Now I need a beer!


----------



## shake1969

Trick question. It's a AV-8B Harrier.


----------



## Fire44

shake1969 said:


> Trick question. It's a AV-8B Harrier.


























Now lets all have a beer!!!!

Gary


----------



## bbuchanan2

Ok, lets look at this question another way. Take a 10 ton block of lead and put it on a set of wheels capable of carrying the weight. Now attach a big jet engine to the top of the block. If this big block of lead were on that same conveyor with the jet engine developing say 10,000 pounds of thrust, and the conveyor was generating an equivalent 10,000 pounds of thrust in the opposing direction would the block move forward down the conveyor? I do believe it would move due to other forces acting upon the block / conveyor such as wind resistance and friction, but it would not move down the conveyor with any significant speed.

When looking at the airplane there is significant more friction than just wheel bearings. As a result of the aircraftâ€™s mass, gravity is pulling the aircraft down onto the conveyor. The friction between the tires and the moving conveyor will reduce the forward movement of the airplane. If all measurement of thrust between the conveyor and airplane are equal, excluding any outside forces such as wind resistance and other non direct friction, the aircraft will not move. Just because it has wings that are capable of overcoming gravity doesnâ€™t mean those wings are working to produce lift with no forward speed, therefore the airplane and the block of lead are going to behave the same.

Try going to an airport with a moving walkway. Take one of those baggage carts and enter the walkway going the wrong direction. You are providing forward thrust to the baggage cart, and the walkway is providing opposing thrust to the baggage cart. Assuming you walk forward at the same speed the walkway is moving in the opposite direction, the baggage cart will not move.


----------



## PDX_Doug

B-Man said:


> Try going to an airport with a moving walkway. Take one of those baggage carts and enter the walkway going the wrong direction. You are providing forward thrust to the baggage cart, and the walkway is providing opposing thrust to the baggage cart. Assuming you walk forward at the same speed the walkway is moving in the opposite direction, the baggage cart will not move.


Again, there is a fundamental difference in the experiment you are proposing, and the question asked. In your experiment, the motive power (your feet) is being applied directly to the moving walkway. This simulates what would happen if you were to, say, drive a car onto the walkway. But in an aircraft, the motive power is applied to the air... not the walkway.

Let's modify your experiment slightly to compensate for this. Again move the baggage cart onto the walkway going the wrong direction. But this time, instead of walking behind the cart (on the moving walkway), move to the side, and walk on the fixed floor beside the moving walkway, holding your arm out to the side to push the cart that is on the moving walkway, and see what happens. You have disconnected the motive force (thrust) acting on the cart from the moving walkway much the same as the thrust from an airplane engine is disconnected from the rolling runway, and you can easily push the cart down the walkway the wrong direction. Give it a try!









Happy Trails,
Doug


----------



## cookie9933

OK. Anyone getting more confused here? Well, I'm not.

Think I'll have another beer.









Bill


----------



## egregg57

This is very easy and this post is driving me nuts.









First get rid of the conveyor. It's a distraction. The wheels sitting on the conveyor will spin when the conveyor moves. The aircraft, for conversation sake, will not move. There is little or no friction. UNLESS you apply the brakes. Yes some friction will cause the aircraft to move with the direction of the conveyorbut that being said....

It doesn't matter if the conveyor is moving 10 miles an hour or 100 miles an hour it's not going to move the aircraft with free spinning wheels and no friction present (currently not possible) on the wheel bearings.

Now throw 10, 20, 30, 40,000lbs of thrust coming from the propulsion system on that aircraft.

That trust is pushing on the aircraft frame, not the wheels. The wheels simply support the aircraft and allow the surface under them to move or the wheels move over that surface. The plane will continue to accelerate forward, regardless of which direction the conveyor is moving. Once the engines have created enough forward speed the wings will generate lift over the airfoil chord and lift will be produced.

it's simple physics folks, can we put this to bed?









Eric


----------



## bbuchanan2

No I cannot simply put this to bed because your argument does not take into effect the very significant friction force between the conveyor and the wheels. If you put any wheeled object with measurable mass on the conveyor and turned the belt on, the object will move backwards with the belt unless another force is applied to resist the friction force applied to the tires by the moving belt. Get in you car and accelerate down a road, then let of the gas and see how the car slows down. This is caused by the friction between the tires and the road (yes wind and driveline friction also contribute.) The same applies to this argument but is magnified by the addition work/force being added by the conveyor.

As to the baggage cart argument you are not taking into consideration the force/thrust your bodyâ€™s muscles are asserting to counteract the force of the walkway. If the cart is on the moving walkway and you are standing beside the walkway holding the cart, but not walking forward I think you will find it takes effort to maintain the cart in a stationary position. So take this effort (which is basically the same as force or thrust) and add to it the additional force applied by your body when walking forward then the equation changes and you are applying more force to the cart than is the moving walkway. The tires/wheels job is to reduce friction, but they do not eliminate it completely.

Now tongue in cheek I will agree that the thrust from the jet engine is more efficiently applying its force to the airplane than is the force being applied by the conveyor, so the airplane will move forward and eventually take off. I would just think it dam sure better be a very long runway.

See now this topic has made me remember all those dam physics classes I took in college, and I had sworn to forget them. And yes I will argue with a fence post, its one of my favorite pastimes.


----------



## PDX_Doug

B-Man said:


> I will agree...
> ...the airplane will move forward and eventually take off.


And all was right with the Universe!









_Thank you everybody! Be sure to try the veal! We'll be here all week! Goodnight!_

Happy Trails,
Doug


----------



## egregg57

I'm done with this silly thing!


----------



## tdvffjohn

I just hope the engine is running enough so I am not going backwards on the conveyor.


----------



## PDX_Doug

egregg57 said:


> I'm done with this silly thing!


Yeah, right!


----------



## wolfwood

tdvffjohn said:


> ....so I am not going backwards on the conveyor.


I don't know nothing about that John (and, Doug, I didn't ask, either







) ....but we do seem to be going backwards in time


----------



## 3LEES

PDX_Doug said:


> _Thank you everybody! Be sure to try the veal! We'll be here all week! Goodnight!_


You forgot to tell them to tip the waiter....









Dan


----------



## skippershe

PDX_Doug said:


> I will agree...
> ...the airplane will move forward and eventually take off.


And all was right with the Universe!









_Thank you everybody! Be sure to try the veal! We'll be here all week! Goodnight!_

Happy Trails,
Doug
[/quote]
















I can't stop laughing!!!!!!


----------



## bentpixel

For $.02 ( or the cost of a balloon) here is a mind experiment: 
 Stand on a conveyor belt. 
Inflate the balloon. 
 Release the balloon. 
Repeat while NOT standing on a conveyor belt.
 Did the balloon leave your hand both times?

End of experiment.


----------



## PDX_Doug

bentpixel said:


> For $.02 ( or the cost of a balloon) here is a mind experiment:
> Stand on a conveyor belt.
> Inflate the balloon.
> Release the balloon.
> Repeat while NOT standing on a conveyor belt.
> Did the balloon leave your hand both times?
> 
> End of experiment.


Never got the chance to find out...
I fell off the end of the conveyor belt before I had the balloon inflated.
I did fly though...

Right up to the point where I hit the ground!









Happy Trails,
Doug


----------



## wolfwood

PDX_Doug said:


> Never got the chance to find out...
> I fell off the end of the conveyor belt before I had the balloon inflated.
> I did fly though...
> 
> Right up to the point where I hit the ground!
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Happy Trails,
> Doug


...and you held onto the balloon even while falling flying? Very good!

So...now you're saying that GRAVITY is involved here, too ????


----------



## PDX_Doug

wolfwood said:


> So...now you're saying that GRAVITY is involved here, too ????


No... Just that the rules didn't allow me to walk in the opposite direction, and at a speed matching that of the conveyor belt, while I blew up the balloon. Now, had I been wearing roller blades...









Happy Trails,
Doug


----------



## wolfwood

PDX_Doug said:


> So...now you're saying that GRAVITY is involved here, too ????


No... Just that the rules didn't allow me to walk in the opposite direction, and at a speed matching that of the conveyor belt, while I blew up the balloon. Now, had I been wearing roller blades...









Happy Trails,
Doug
[/quote]
In fact, the 'rules' never said the conveyor belt was moving








Would that be "wearing roller blades" while sitting....or standing ????

...and would it matter if the wind turbine to your left is 5ft taller than the one on your right?


----------



## PDX_Doug




----------



## Scoutr2

The plane will take off. The thrust from the engine will move the plane forward, regardless of what the wheels and the runway (belt) is doing, unless the pilot is applying the brakes (which is not stated in the problem).

Think of it this way - once the plane takes off and the wheels leave the ground, does it matter what the wheels are doing? (I HOPE you answer NO to this.) It doesn't matter on the ground, either!

Now, on to the tree. This is one that is just a matter of symantics. When the tree falls, it disturbs the air arouind it, which causes vibration waves that move through the air. Our ear drum reacts, or vibrates at the same frequency as the vibrations in the air (same as a mechanical device, such as a microphone, which also reacts to those vibrations). Our brain interprets those vibrations into what we define as "sound." So if there is no person, animal, or device in the forest to recieve the vibrations, then there is no sound. The vibrations are still there - it's just that nothing is there to interpret the vibrations.

But even better - "If a man speaks in a forest and there is no woman there to hear him, is he still wrong?"









THAT is the $.02 question!!!

Mike


----------



## Oregon_Camper

Scoutr2 said:


> But even better - "If a man speaks in a forest and there is no woman there to hear him, is he still wrong?"


ROTFLMAO!!!!


----------



## PDX_Doug

Oregon_Camper said:


> But even better - "If a man speaks in a forest and there is no woman there to hear him, is he still wrong?"


ROTFLMAO!!!!








[/quote]
X2

How very, very true.









Happy Trails,
Doug


----------



## RizFam

PDX_Doug said:


> But even better - "If a man speaks in a forest and there is no woman there to hear him, is he still wrong?"


ROTFLMAO!!!!








[/quote]
X2

How very, very true.









Happy Trails,
Doug
[/quote]

Now Now Easy Boys







Back to the discussion on hand









It will not take off














Sorry Doug


----------



## tdvffjohn

Scoutr2 said:


> Now, on to the tree. This is one that is just a matter of symantics. When the tree falls, it disturbs the air arouind it, which causes vibration waves that move through the air. Our ear drum reacts, or vibrates at the same frequency as the vibrations in the air (same as a mechanical device, such as a microphone, which also reacts to those vibrations). Our brain interprets those vibrations into what we define as "sound." So if there is no person, animal, or device in the forest to recieve the vibrations, then there is no sound. The vibrations are still there - it's just that nothing is there to interpret the vibrations.
> 
> Mike


Just because there is nothing to interpret the vibrations, are you saying there is no sound


----------



## wolfwood

> "If a man speaks in a forest and there is no woman there to hear him, is he still wrong?"





tdvffjohn said:


> Just because there is nothing to interpret the vibrations, are you saying there is no sound


There doesn't need to be any sound, nor does there need to be anyone there to hear him if there _is_ a sound. No doubt - _he_ will still be wrong!


----------



## RizFam

wolfwood said:


> Just because there is nothing to interpret the vibrations, are you saying there is no sound


There doesn't need to be any sound, nor does there need to be anyone there to hear him if there _is_ a sound. No doubt - _he_ will still be wrong!








[/quote]


----------



## skippershe

RizFam said:


> Just because there is nothing to interpret the vibrations, are you saying there is no sound


There doesn't need to be any sound, nor does there need to be anyone there to hear him if there _is_ a sound.  No doubt - _he_ will still be wrong!








[/quote]









[/quote]
Yeah! So there!


----------



## wolfwood

skippershe said:


> Just because there is nothing to interpret the vibrations, are you saying there is no sound


There doesn't need to be any sound, nor does there need to be anyone there to hear him if there _is_ a sound. No doubt - _he_ will still be wrong!







[/quote]







[/quote]
Yeah! So there!







[/quote]
I heard that !!!!! 
(oooh ooooh oooooh Good Vibrations.......)

x2

..... and the women were BOTH right!!!!


----------



## skippershe

wolfwood said:


> Just because there is nothing to interpret the vibrations, are you saying there is no sound


There doesn't need to be any sound, nor does there need to be anyone there to hear him if there _is_ a sound. No doubt - _he_ will still be wrong!







[/quote]







[/quote]
Yeah! So there!







[/quote]
I heard that !!!!! 
(oooh ooooh oooooh Good Vibrations.......)

x2

..... and the women were BOTH right!!!!








[/quote]
Who'd want to listen to _him _ anyway??


----------



## tdvffjohn

Did 'she' make a sound????? I did not hear anything


----------



## Oregon_Camper

skippershe said:


> Who'd want to listen to _him _ anyway??


We're you two talking about something?


----------



## RizFam

Oregon_Camper said:


> Who'd want to listen to _him _ anyway??


We're you two talking about something?








[/quote]

Did 'she' make a sound????? I did not hear anything [/quote]

& you too John


----------



## wolfwood

tdvffjohn said:


> Did 'she' make a sound????? I did not hear anything


----------



## renegade21rs

After twelve pages, the answer is no. No, no, a thousand times, NO! The plane is STATIONARY! It CANNOT take off if it is NOT MOVING!


----------



## RizFam

renegade21rs said:


> After twelve pages, the answer is no. No, no, a thousand times, NO! The plane is STATIONARY! It CANNOT take off if it is NOT MOVING!


Exactly! That is what I said









Now what were we girls chatting about?


----------



## wolfwood

RizFam said:


> After twelve pages, the answer is no. No, no, a thousand times, NO! The plane is STATIONARY! It CANNOT take off if it is NOT MOVING!


Exactly! That is what I said









Now what were we girls chatting about?







[/quote]
Hey! Did we ever get that ClubHouse finished? Seems to me the last I recall, we were waiting on one of the guys to do something usefull







WHAT were we thinking!!!?????

btw, Tami....your InBox is full


----------



## RizFam

wolfwood said:


> After twelve pages, the answer is no. No, no, a thousand times, NO! The plane is STATIONARY! It CANNOT take off if it is NOT MOVING!


Exactly! That is what I said









Now what were we girls chatting about?







[/quote]
Hey! Did we ever get that ClubHouse finished? Seems to me the last I recall, we were waiting on one of the guys to do something usefull







WHAT were we thinking!!!?????

btw, Tami....your InBox is full








[/quote]








I forgot about the clubhouse







where is MaeJae








Inbox cleared ...........thanx


----------



## PDX_Doug

renegade21rs said:


> After twelve pages, the answer is no. No, no, a thousand times, NO! The plane is STATIONARY! It CANNOT take off if it is NOT MOVING!


Who said the plane isn't moving? I didn't see anything in the question that said the plane isn't moving.









Happy Trails,
Doug


----------



## Oregon_Camper

PDX_Doug said:


> After twelve pages, the answer is no. No, no, a thousand times, NO! The plane is STATIONARY! It CANNOT take off if it is NOT MOVING!


Who said the plane isn't moving? I didn't see anything in the question that said the plane isn't moving.









Happy Trails,
Doug
[/quote]

It is just on the tread mill gaining speed right....then, up Up UP and away.


----------



## egregg57

I love this post! Garethsdad asked about it so....! Ha! Here ya go!! Let the misery begin!!

Eric


----------



## 3LEES




----------



## Lady Di

Oh nooooo...!

Not the 'conveyor belt'.


----------



## PDX_Doug

*I'm baaaaack!*


----------



## tdvffjohn

Wonder if they serve drinks on that flight.??


----------



## Katrina

Eric should be taken out back and shot.
He's a mean evil man!!!!


----------



## GarethsDad

Now that I've read the whole thing to this point I must say that you do not need wheels to fly. In the mid 1950's Goodyear made a Inflatoplane with the idea that it could be used by the military as a rescue plane that had a 2 stroke enging that you tied to a tree, gunned the engine and it would hover off the ground decreasing the need for a long runway. James


----------



## 2500Ram

Time for round two


----------



## Thor

PDX

It looks like it is time to play again.
















The Plane would not take off. You need air flow over the wings for lift. If it were that easy all aircraft carriers would be equiped with conveyor belts. Imagine how much shorter the carrier would be.

You maybe able to state that a prop plane with enough horsepower and large enough prop may push enough air over the wings to create lift while the plane is stationary.

Thor


----------



## webeopelas

Thor said:


> PDX
> 
> It looks like it is time to play again.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> The Plane would not take off. You need air flow over the wings for lift. If it were that easy all aircraft carriers would be equiped with conveyor belts. Imagine how much shorter the carrier would be.
> 
> You maybe able to state that a prop plane with enough horsepower and large enough prop may push enough air over the wings to create lift while the plane is stationary.
> 
> Thor


BINGO! Even though the question is framed to allow any interpretation you would like, if you suppose a treadmill cannot hover in midair or travel at the same speed of the aircraft, it is very obvious that even though the planes wheels are moving, the plane is not, therefore no airflow means no lift.


----------



## Fire44

More importantly....if a TV and a Outback are on the "treadmill" will they still get to the rally in time for the first round of beer????


----------



## egregg57

I love this Thread!! I just Love it!!


----------



## Doxie-Doglover-Too

Fire44 said:


> More importantly....if a TV and a Outback are on the "treadmill" will they still get to the rally in time for the first round of beer????


never , NEVER underestimate the power of an Outbacker with intentions of getting to a rally and a beer..........


----------



## PDX_Doug

Thor said:


> The Plane would not take off. You need air flow over the wings for lift. If it were that easy all aircraft carriers would be equiped with conveyor belts. Imagine how much shorter the carrier would be.


Actually Thor, they are... But the Navy calls them steam catapults. And you are right, they do make for a much shorter runway.









PLAY BALL!

Happy Trails,
Doug


----------



## BoaterDan

These are the undeniable facts. These have all been explained previously in this thread, but I see answers over and over again that deny physics.

1. Planes fly as a result of airflow over the wings (providing lift), PERIOD.
2. A plane need not be moving relative to the ground in order for there to be airflow over the wings. Anybody who has flown a kite knows this. Planes fly in wind tunnels all the time. A plane flying at 100 mph air speed into 100 mph headwind would appear to be hovering relative to the ground, but it would still be flying.
3. Now, here's the hard one... the wheels have nothing significant to do with any of this, as a plane doesn't gain or maintain airspeed as a result of any force applied to its wheels. Wheels are necessary only because planes typically take off on the ground from a standstill, and therefore must roll forward until they gain enough airflow over the wings.

The logical conclusion is that no force applied to the wheels to make them spin can make the plane fly or keep it from flying.

Now, from these facts we've gone off on some arguments which are really just variations in interpretations of the original question, and some which just defy the simple physics of flight. Most that deny the plane will fly seem to be stuck in comparisons to totally different paradigms focused on the wheels as the point where force is applied. The carrier launch is a perfect example of how irrelevant the wheels are as a force application point. (Not irrelveant to the launch process as a whole, of course, but they are really just going along for the ride to make it easier to move the plane forward until it gains sufficient speed through the air. Carriers also launch into the wind for the same purpose.)

The most common interpretation I see is the assumption that the plane is not moving forward. I don't think the original question really indicates that is the case. Certainly the plane would not fly if it can't generate airflow, but the conveyor doesn't necessarily prohibit that.


----------



## egregg57

PDX_Doug said:


> The Plane would not take off. You need air flow over the wings for lift. If it were that easy all aircraft carriers would be equiped with conveyor belts. Imagine how much shorter the carrier would be.


Actually Thor, they are... But the Navy calls them steam catapults. And you are right, they do make for a much shorter runway.









PLAY BALL!

Happy Trails,
Doug
[/quote]

Oh, Just a note on that, with 30+ Knots forward speed and a good head wind, lets say in a storm, (Which has occured) there is enough velocity over the wings to create a significant and dangerous amount of lift. We used 12 point, 24 point and when its real bad 36 point tie downs (Chains) to keep the planes on the deck.


----------



## renegade21rs

Please. Come on. Think about this, but not for more than a minute, okay?









14 pages. Sheesh!


----------



## Thor

PDX_Doug said:


> Actually Thor, they are... But the Navy calls them steam catapults. And you are right, they do make for a much shorter runway.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> PLAY BALL!
> 
> Happy Trails,
> Doug


Doug you forgot about the conveyor belt.









Thor


----------



## PDX_Doug

Thor said:


> Actually Thor, they are... But the Navy calls them steam catapults. And you are right, they do make for a much shorter runway.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> PLAY BALL!
> 
> Happy Trails,
> Doug


Doug you forgot about the conveyor belt.









Thor
[/quote]

Thor,

I will never, EVER, forget about the conveyor belt! It is indelibly seared into my brain for the rest of my life, thank you very much!

Happy Trails,
Doug


----------



## BoaterDan

Hey, let me pose a question that might make some people think about this in a different way.

Suppose a plane is flying along at 1,000 feet. The pilot manages to reach his hand out the window and give the left wheel a big spin backward, while the copilot does the same for the other one. In fact, they're able to keep the wheels spinning backward at what would be 100mph if the plan were on the ground.

Would that have any significant effect whatsoever on the plane flying?


----------



## renegade21rs

BoaterDan said:


> Hey, let me pose a question that might make some people think about this in a different way.
> 
> Suppose a plane is flying along at 1,000 feet. The pilot manages to reach his hand out the window and give the left wheel a big spin backward, while the copilot does the same for the other one. In fact, they're able to keep the wheels spinning backward at what would be 100mph if the plan were on the ground.
> 
> Would that have any significant effect whatsoever on the plane flying?


Yes! The plane would crash because the pilot and the copilot fell out !


----------



## Zymurgist

Fire44 said:


> More importantly....if a TV and a Outback are on the "treadmill" will they still get to the rally in time for the first round of beer????


Doesn't matter, the beer is in my Outback.


----------



## Zymurgist

If the wheels are turning, then the conveyor belt will move in the opposite direction to match the wheel rotation, thus making the net rotation zero. If the wheels are rotating (or trying to rotate), the plane is moving, when it reaches rotation velocity it's going to fly.

If a plane was at the end of a runway of pure zamboni cleaned ice, went to full throttle with the parking brakes engaged, (assuming the plane moves forward in a straight line) it too will take off and the wheels will not be turning.


----------



## GlenninTexas

On a related note,

If a generator is running in the woods, but there is no one around to hear it, does it make too much noise?































Regards, Glenn


----------



## BoaterDan

GlenninTexas said:


> On a related note,
> 
> If a generator is running in the woods, but there is no one around to hear it, does it make too much noise?
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Regards, Glenn


Yes, and the DNR writes you a ticket for leaving it there.


----------



## Oregon_Camper

PDX_Doug said:


> Actually Thor, they are... But the Navy calls them steam catapults. And you are right, they do make for a much shorter runway.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> PLAY BALL!
> 
> Happy Trails,
> Doug


Doug you forgot about the conveyor belt.









Thor
[/quote]

Thor,

I will never, EVER, forget about the conveyor belt! It is indelibly seared into my brain for the rest of my life, thank you very much!

Happy Trails,
Doug
[/quote]

someone needs to send the two of you to your rooms and not let you out until we come to a conclusion on this....


----------



## Thor

LMAO
















We need a new one

Thor


----------



## Oregon_Camper

Thor said:


> LMAO
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> We need a new one
> 
> Thor


Appears from your sig picture that you have plenty of room (2 Outbacks!!)


----------



## bikerdude&dudette

GlenninTexas said:


> On a related note,
> 
> If a generator is running in the woods, but there is no one around to hear it, does it make too much noise?
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Regards, Glenn


but more important, is it still the mans fault for leaving it there to go get more beer??
and my $0.02 says the key words here are "there is no wind" so we must ask, is it a jet or a prop job??
good luck
steve


----------



## Fire44

I think we are going to find out on 1/30/08 if the plane will takeoff or not:

http://dsc.discovery.com/video/?playerId=2...tleId=348411075

Cick on link scroll down the list on the left to "60 clips"...

Click on "60 clips" and you will see "Plane on Treadmill"

You will have to watch one commercial but they give you a run down of what they are going to do!!!

I will consider taking bets....I say the plane will NOT leave the runway!!!

Gary


----------



## Moosegut

I just set my calendar for 1/30. My bet is - it will take off. There will be no air over the wings as stated - until, of course, the propeller provides the forward thrust needed to get the plane moving.

Hmmm, now we all have to think of something good to bet that will enable everyone across the country to partake. Maybe winners get gold stars next to their screen names or something.


----------



## PDX_Doug

Oh boy! This is gonna be fun! I'll be setting the TIVO for this one, for sure. I want to be sure I have a copy for Thor, when he conveniently, um, misses the episode.

Just to clarify... You want to scroll down to, and click on "MythBusters", then to the right of MythBusters, click on "60 Clips".

Happy Trails,
Doug


----------



## Oregon_Camper

PDX_Doug said:


> Oh boy! This is gonna be fun! I'll be setting the TIVO for this one, for sure. I want to be sure I have a copy for Thor, when he conveniently, um, misses the episode.
> 
> Just to clarify... You want to scroll down to, and click on "MythBusters", then to the right of MythBusters, click on "60 Clips".
> 
> Happy Trails,
> Doug


Looks like (after >200 posts) we'll have our answer. Seems like a poll is in order to allow everyone to place their bet. ...I'm on it.


----------



## BoaterDan

I hope they've done it right. The magic point that I hope isn't missed is that the conveyor doesn't keep the plane from moving. The clip shows them holding the model plane on a short treadmill. I hope they're not going to try to see if they can get the plane to just lift off vertically like a Harrier!

We all agree (at least I do) that the plane needs to move forward to fly. The point we've tried to make is simply that the conveyor doesn't have any impact on whether or not that happens.


----------



## egregg57

I love this thread!


----------



## Oregon_Camper

egregg57 said:


> I love this thread!


I agree...

Not sure what it will take to get another thread like this one. Great posts...great debate...great fun!!


----------



## PDX_Doug

Well, if you guys feel like you are up for another one...









Happy Trails,
Doug


----------



## Oregon_Camper

PDX_Doug said:


> Well, if you guys feel like you are up for another one...
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Happy Trails,
> Doug


What ya thinking? We're always up for some fun.


----------



## bpedrotty

PDX Doug wrote:

"Actually Thor, they are... But the Navy calls them steam catapults. And you are right, they do make for a much shorter runway.







"

I hate it when I come late to the party...

PDX Doug,

The key difference between the cat and the conveyor is that the cat accelerates the jet (and the periodic E-2) through the air mass (in fact requiring a certain amount of wind already coming over the deck to get the A/C up to speed) in order to get enough wind over the wings to take off. The conveyor belt is going to specifically prevent the plane from generating forward momentum through the air mass. No air flow over the wings = no take off.

Only in some rare applications is the thrust to weight ratio enough over 1:1 that an A/C can take off without lift to the wings. The Harrier uses ducted exhaust to achieve this while helicopters and the Osprey use the spinning of the air foil (Pure Freak'in Magic) to generate lift and thus take off. I would be very surprised if a piston driven engine could produce enough lift via airfoil (short stubby prop blades) or thrust to weight advantage to overcome lack of airflow over the wings.

All that said, I just fly them, I don't build them and my degree is in geography...

Walleye


----------



## PDX_Doug

walleye said:


> PDX Doug wrote:
> 
> "Actually Thor, they are... But the Navy calls them steam catapults. And you are right, they do make for a much shorter runway.
> 
> 
> 
> 
> 
> 
> 
> "
> 
> I hate it when I come late to the party...
> 
> PDX Doug,
> 
> The key difference between the cat and the conveyor is that the cat accelerates the jet (and the periodic E-2) through the air mass (in fact requiring a certain amount of wind already coming over the deck to get the A/C up to speed) in order to get enough wind over the wings to take off. The conveyor belt is going to specifically prevent the plane from generating forward momentum through the air mass. No air flow over the wings = no take off.


You are correct, walleye. However in the statement I made above, I was not assuming the conveyor belt would be fighting the plane (as some think the original question indicates), but that by traveling in the the same direction, the belt and the cats are fundamentally the same. Of course, in the case of the conveyor belt, the pilot would have to have his brakes locked, thus remaining stationary relative to the belt (the same as he is relative to the hook on the cat).

Happy Trails,
Doug


----------



## N7OQ

You people need to stop thinking of a airplane like a car, cars, bikes, trucks spin their tires to move forward and they would sit still if on a conveyor moving the same speed. A airplane used thrust from the engine to move forward. there is even a pilot who thinks it will not take off







( I hope I never ride on any plane we is flying







) *Its a trick question people* I already know the answer Mythbusters proved it would takeoff, I can't believe how many people are arguing over the same question, there are a bunch of forums in the internet debating this same subject.


----------



## bpedrotty

PDX_Doug said:


> PDX Doug wrote:
> 
> "Actually Thor, they are... But the Navy calls them steam catapults. And you are right, they do make for a much shorter runway.
> 
> 
> 
> 
> 
> 
> 
> "
> 
> I hate it when I come late to the party...
> 
> PDX Doug,
> 
> The key difference between the cat and the conveyor is that the cat accelerates the jet (and the periodic E-2) through the air mass (in fact requiring a certain amount of wind already coming over the deck to get the A/C up to speed) in order to get enough wind over the wings to take off. The conveyor belt is going to specifically prevent the plane from generating forward momentum through the air mass. No air flow over the wings = no take off.


You are correct, walleye. However in the statement I made above, I was not assuming the conveyor belt would be fighting the plane (as some think the original question indicates), but that by traveling in the the same direction, the belt and the cats are fundamentally the same. Of course, in the case of the conveyor belt, the pilot would have to have his brakes locked, thus remaining stationary relative to the belt (the same as he is relative to the hook on the cat).

Happy Trails,
Doug
[/quote]
PDX Doug,

You are correct that I am assuming the conveyor belt is running in the opposite direction of travel from the airplane (plane going east, conveyor running west). As N70Q has graciously pointed out, I am apparently an idiot.


----------



## N7OQ

walleye said:


> PDX Doug wrote:
> 
> "Actually Thor, they are... But the Navy calls them steam catapults. And you are right, they do make for a much shorter runway.
> 
> 
> 
> 
> 
> 
> 
> "
> 
> I hate it when I come late to the party...
> 
> PDX Doug,
> 
> The key difference between the cat and the conveyor is that the cat accelerates the jet (and the periodic E-2) through the air mass (in fact requiring a certain amount of wind already coming over the deck to get the A/C up to speed) in order to get enough wind over the wings to take off. The conveyor belt is going to specifically prevent the plane from generating forward momentum through the air mass. No air flow over the wings = no take off.


You are correct, walleye. However in the statement I made above, I was not assuming the conveyor belt would be fighting the plane (as some think the original question indicates), but that by traveling in the the same direction, the belt and the cats are fundamentally the same. Of course, in the case of the conveyor belt, the pilot would have to have his brakes locked, thus remaining stationary relative to the belt (the same as he is relative to the hook on the cat).

Happy Trails,
Doug
[/quote]
PDX Doug,

You are correct that I am assuming the conveyor belt is running in the opposite direction of travel from the airplane (plane going east, conveyor running west). As N70Q has graciously pointed out, I am apparently an idiot.
[/quote]

Hold it now I never said anyone was a Idiot. Half the people in this country disagree with the answer including the DW and half the guy's I work with. I don't think any of them are idiots, they are wrong but not idiots.


----------



## cookie9933

Fire44 said:


> I think we are going to find out on 1/30/08 if the plane will takeoff or not:
> 
> http://dsc.discovery.com/video/?playerId=2...tleId=348411075


Hopefully, that test (or whatever it may be) will be definitive and establish once and for all that the plane WILL take off. That was my immediate take on this when the question first surfaced on Outbackers. I guess either you get it or you don't.









Bill


----------



## Oregon_Camper

walleye said:


> You are correct that I am assuming the conveyor belt is running in the opposite direction of travel from the airplane (plane going east, conveyor running west). As N70Q has graciously pointed out, I am apparently an idiot.


I'm not an Moderator on this board, but please refrain from innuendos. I don't see where N70Q said anything like that. This entire thread has been in fun...let's not take it down the wrong path.

...now back to having fun.


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## PDX_Doug

Nope, no idiots here. A few misguided souls on this topic (







), but not an idiot in the bunch.
I don't believe N70Q intended such a suggestion in his comments.

Happy Trails,
Doug


----------



## raynardo

Well, here's my thought on the subject (not so much as a thought but rather an observation):

If this really would allow the plane enough lift to take-off (the big conveyor belt), then this would be the greatest thing in the world for the decks of aircraft carriers. Since the Navy doesn't use these, and I'm guessing they're pretty smart and would have figured this out in the last 80 years, I'm guessing it doesn't work.

Lift is generate by the velocity (speed) of the wind over and under the wings. Unless the plane can attain the equivalent of take-off speed, to achieve the lift that it needs, it won't fly.

I'll be covering all bets for you on Mythbusters, send your bet to:


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## BoaterDan

raynardo said:


> Well, here's my thought on the subject (not so much as a thought but rather an observation):
> 
> If this really would allow the plane enough lift to take-off (the big conveyor belt), then this would be the greatest thing in the world for the decks of aircraft carriers. Since the Navy doesn't use these, and I'm guessing they're pretty smart and would have figured this out in the last 80 years, I'm guessing it doesn't work.
> 
> Lift is generate by the velocity (speed) of the wind over and under the wings. Unless the plane can attain the equivalent of take-off speed, to achieve the lift that it needs, it won't fly.
> 
> I'll be covering all bets for you on Mythbusters, send your bet to:


Ah... finally somebody who agrees on the simple truth that the plane needs forward motion to have airflow over the wings to generate lift... but comes to the wrong conclusion.

Raynardo, since the plane does not use the wheels to apply acceleration, how does their spinning from the contact with the conveyor belt keep the plane from achieving the necessary forward speed?

As I said, I've not heard any of us that believe the plane will fly suggest that it will lift off vertically. No, it will still accelerate to the take-off speed and then roll off just like normal. The conveyor is simply and utterly irrelevant.


----------



## GlenninTexas

BoaterDan is absolutely correct. The conveyor belt is actually irrelelent to the equation. Forward speed will be achieved, and the plane will lift off.

Regards, Glenn


----------



## raynardo

BoaterDan said:


> Ah... finally somebody who agrees on the simple truth that the plane needs forward motion to have airflow over the wings to generate lift... but comes to the wrong conclusion.
> 
> Raynardo, since the plane does not use the wheels to apply acceleration, how does their spinning from the contact with the conveyor belt keep the plane from achieving the necessary forward speed?
> 
> As I said, I've not heard any of us that believe the plane will fly suggest that it will lift off vertically. No, it will still accelerate to the take-off speed and then roll off just like normal. The conveyor is simply and utterly irrelevant.


I agree 100% that an airplane doesn't need it's wheels to take off, float plane and ski planes as well VTOL planes dramatically prove this point.

But somehow I was under the impression that the conveyor belt moved by a mechanical means other than power supplied by the airplane. In and by itself, I realize that the airplane has no ability to move the conveyor belt.

So, if the conveyor belt is not moved by an outside force to equal the speed the airplane needs to take off, then the conveyor won't move, and it won't make a difference -- it will just be an expensive runway -- and the airplane will take off.

Maybe I read more into the problem than there really was.

Hopefully this makes sense.


----------



## H2oSprayer

GlenninTexas said:


> Forward speed will be achieved, and the plane will lift off.


If the thrust generated by the plane matches the speed of the conveyor belt moving on the opposite direction, I agree that the tires of the plane will be spinning, but the plane will be sitting at a standstill. Where will the forward speed come from?


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## MaeJae

Wow!!!! If they'd only known!
What a conveyor belt was ...










BTW... I DON'T think it will fly









MaeJae


----------



## 3LEES

raynardo said:


> Ah... finally somebody who agrees on the simple truth that the plane needs forward motion to have airflow over the wings to generate lift... but comes to the wrong conclusion.
> 
> Raynardo, since the plane does not use the wheels to apply acceleration, how does their spinning from the contact with the conveyor belt keep the plane from achieving the necessary forward speed?
> 
> As I said, I've not heard any of us that believe the plane will fly suggest that it will lift off vertically. No, it will still accelerate to the take-off speed and then roll off just like normal. The conveyor is simply and utterly irrelevant.


I agree 100% that an airplane doesn't need it's wheels to take off, float plane and ski planes as well VTOL planes dramatically prove this point.

But somehow I was under the impression that the conveyor belt moved by a mechanical means other than power supplied by the airplane. In and by itself, I realize that the airplane has no ability to move the conveyor belt.

So, if the conveyor belt is not moved by an outside force to equal the speed the airplane needs to take off, then the conveyor won't move, and it won't make a difference -- it will just be an expensive runway -- and the airplane will take off.

Maybe I read more into the problem than there really was.

Hopefully this makes sense.
[/quote]
It does make sense...except for the statement that the conveyor will not move. The wheels will not move, but the conveyor *will* due to the force of the propeller. The plane *will* attain sufficient airspeed to lift off the runway/conveyor.


----------



## H2oSprayer

3LEES said:


> Ah... finally somebody who agrees on the simple truth that the plane needs forward motion to have airflow over the wings to generate lift... but comes to the wrong conclusion.
> 
> Raynardo, since the plane does not use the wheels to apply acceleration, how does their spinning from the contact with the conveyor belt keep the plane from achieving the necessary forward speed?
> 
> As I said, I've not heard any of us that believe the plane will fly suggest that it will lift off vertically. No, it will still accelerate to the take-off speed and then roll off just like normal. The conveyor is simply and utterly irrelevant.


I agree 100% that an airplane doesn't need it's wheels to take off, float plane and ski planes as well VTOL planes dramatically prove this point.

But somehow I was under the impression that the conveyor belt moved by a mechanical means other than power supplied by the airplane. In and by itself, I realize that the airplane has no ability to move the conveyor belt.

So, if the conveyor belt is not moved by an outside force to equal the speed the airplane needs to take off, then the conveyor won't move, and it won't make a difference -- it will just be an expensive runway -- and the airplane will take off.

Maybe I read more into the problem than there really was.

Hopefully this makes sense.
[/quote]
It does make sense...except for the statement that the conveyor will not move. The wheels will not move, but the conveyor *will* due to the force of the propeller. The plane *will* attain sufficient airspeed to lift off the runway/conveyor.
[/quote]

I was under the impression that on the Mythbusters, the conveyor was going to be hooked up to a vehicle that was going to be pulling it in the opposite direction. Is that correct? If so, how will the propeller cause the conveyor belt to move?


----------



## Oregon_Camper

We been talking about this for sooooo long I'm not sure what the real setup is...


----------



## 3LEES

H2oSprayer said:


> Ah... finally somebody who agrees on the simple truth that the plane needs forward motion to have airflow over the wings to generate lift... but comes to the wrong conclusion.
> 
> Raynardo, since the plane does not use the wheels to apply acceleration, how does their spinning from the contact with the conveyor belt keep the plane from achieving the necessary forward speed?
> 
> As I said, I've not heard any of us that believe the plane will fly suggest that it will lift off vertically. No, it will still accelerate to the take-off speed and then roll off just like normal. The conveyor is simply and utterly irrelevant.


I agree 100% that an airplane doesn't need it's wheels to take off, float plane and ski planes as well VTOL planes dramatically prove this point.

But somehow I was under the impression that the conveyor belt moved by a mechanical means other than power supplied by the airplane. In and by itself, I realize that the airplane has no ability to move the conveyor belt.

So, if the conveyor belt is not moved by an outside force to equal the speed the airplane needs to take off, then the conveyor won't move, and it won't make a difference -- it will just be an expensive runway -- and the airplane will take off.

Maybe I read more into the problem than there really was.

Hopefully this makes sense.
[/quote]
It does make sense...except for the statement that the conveyor will not move. The wheels will not move, but the conveyor *will* due to the force of the propeller. The plane *will* attain sufficient airspeed to lift off the runway/conveyor.
[/quote]

I was under the impression that on the Mythbusters, the conveyor was going to be hooked up to a vehicle that was going to be pulling it in the opposite direction. Is that correct? If so, how will the propeller cause the conveyor belt to move?
[/quote]
This is the original question:

"Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation. 
There is no wind.

Can the plane take off?"

I read this as the conveyor is not powered...just designed to move when the wheels move. If you placed a teathered car on this conveyor and then engaged the wheels, the conveyor would move. If you un-teathered the car, the conveyor would move, but the car would stay stationary.

However, a plane does not have powered wheels. When the force of the propeller starts the movement of the wheels, the conveyor belt would counter the rotation of the wheels. This counter rotation of the conveyor would be in the direction of the front of the plane. The faster the propeller turns, the move counter rotation is needed to "match" the wheels of the plane. The wheels want to rotate, but can't due to the "matching" speed of the conveyor. Thus the plane is sent whizzing down the runway on a counter-rotating conveyor belt and finally reaches airspeed sufficient to lift off the conveyor.


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## NobleEagle

After reading the original post many times and reading all 7 pages of replies. I had to finally chime in on this one. Being a former Air Traffic Controller, I had an interest in the physics of this "brain teaser". I agree 100% that the propeller does not produce wind over the wings to create lift, it only produces forward propulsion to create forward speed which in turn will eventually get enough air to flow over the wing to create lift. I am getting off the topic though. I had to re-read the original post in which the answer is in the last sentence:

Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. *The conveyor belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.* 
There is no wind.

Can the plane take off?

Under the premise that the conveyor belt is traveling at the same speed as the wheels IN THE OPPOSITE DIRECTION OF ROTATION OF THE WHEELS that would mean the plane is now being launched at twice the speed of the wheel travel. That in addition of the propeller providing forward propulsion once the wheels leave the ground, would assist in takeoff and continued flight. At least "thats what I think". (By the way....check out the wonderful artwork posted previously. At first I thought it was incorrect but it is exactly right. It would produce twice the forward speed of the plane.)


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## Oregon_Camper

if the conveyor belt is moving is a direction to stop the wheel from turning (matching speed) then there is no lift...plane will not take off.


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## BoaterDan

Folks, planes don't accelerate by applying force to the wheels, so it doesn't matter one single bit whether the conveyor belt is moving in the same direction as the plane or in the opposite... all that will affect is how fast the wheels are spinning, which has NOTHING whatsoever to do with whether or not the plane takes off.

The detail of the conveyor moving under the wheels is simply a distraction that turns a simple physics equation into a trick question. The author of the question must be rolling on the floor laughing every time the debate launches off into an argument about which way the conveyor is moving.

_Man_, this is fun!


----------



## NobleEagle

Okay, I will own up to it when I am wrong. I posted my thoughts above and had to reconsider. My post above is right if there were powered wheels, it would launch at twice the speed, however, the wheels without power are now freewheeling and the plane would sit still but use alot of fuel doing so. Without wind or forward propulsion, there is not enough air flow over the wing to create lift. I admit I may have been over thinking and typing too fast while trying to figgure it out, but something as simple as forgetting the wheels are not power driven can mess everything up.








boy this is fun lol. Just don't have too much fun or this topic may be closed because the plane takeing off has nothing to do with camping.


----------



## BoaterDan

NobleEagle said:


> ...Just don't have too much fun or this topic may be closed because the plane takeing off has nothing to do with camping.


Ok, so if you take off your wheel chocks when your trailer is parked on a hill, will it _FLY_ over the side of the cliff or will the tongue jack dig into the ground and save it?

Oh, that's not a brain teaser, that's a horrible flashback.







Sorry.


----------



## NobleEagle

BoaterDan said:


> ...Just don't have too much fun or this topic may be closed because the plane takeing off has nothing to do with camping.


Ok, so if you take off your wheel chocks when your trailer is parked on a hill, will it _FLY_ over the side of the cliff or will the tongue jack dig into the ground and save it?

Oh, that's not a brain teaser, that's a horrible flashback.







Sorry.
[/quote]
ROFLMAO! Well you mentioned camping. I would imagine that this may now qualify. But I wont make that call, we have moderators for that.


----------



## Moosegut

Hmmm - seems that if a mistake is made and something erroneous is posted, the only way to delete it is to go back and delete the text.


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## Moosegut

BoaterDan said:


> Okay, I will own up to it when I am wrong. I posted my thoughts above and had to reconsider. My post above is right if there were powered wheels, it would launch at twice the speed, however, the wheels without power are now freewheeling and the plane would sit still but use alot of fuel doing so.
> 
> 
> 
> 
> 
> 
> 
> 
> boy this is fun lol.


Gee, and I thought you had it Noble.







FREEWHEELING is the operative phrase. Boaterdan is absolutely correct - the wheels are thrown in as a distraction. FREEWHEELING MEANS *FREEWHEELING*. If the wheels do *ANYTHING* to impede the forward propulsion generated by the thrust of the engine - THEY ARE NOT FREEWHEELING.


----------



## NobleEagle

Moosegut said:


> Hmmm - seems that if a mistake is made and something erroneous is posted, the only way to delete it is to go back and delete the text.


I knew I was incorrect and was thinking of deleting my original post. However, I will own up when I am wrong and by deleting it, it may have seemed like I was running scared from criticism. I don't run scared







So, I figured it would be better if I posted the fact that I stand corrected


----------



## Moosegut

NobleEagle said:


> Hmmm - seems that if a mistake is made and something erroneous is posted, the only way to delete it is to go back and delete the text.


I knew I was incorrect and was thinking of deleting my original post. However, I will own up when I am wrong and by deleting it, it may have seemed like I was running scared from criticism. I don't run scared







So, I figured it would be better if I posted the fact that I stand corrected








[/quote]

Ohhh, I wasn't talking about you - I was talking about ME. As I was in the middle of typing, I somehow posted a bunch of junk (all kinds of carriage returns and stuff in there) and then started a new response (which I posted) without realizing I had posted the other junker. When I saw it, I wanted to delete it, but couldn't. So, I just edited it and posted that little blurb instead.

Sorry for the confusion.

Scott


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## PDX_Doug

Moosegut said:


> Hmmm - seems that if a mistake is made and something erroneous is posted, the only way to delete it is to go back and delete the text.


I knew I was incorrect and was thinking of deleting my original post. However, I will own up when I am wrong and by deleting it, it may have seemed like I was running scared from criticism. I don't run scared







So, I figured it would be better if I posted the fact that I stand corrected








[/quote]

Ohhh, I wasn't talking about you - I was talking about ME. As I was in the middle of typing, I somehow posted a bunch of junk (all kinds of carriage returns and stuff in there) and then started a new response (which I posted) without realizing I had posted the other junker. When I saw it, I wanted to delete it, but couldn't. So, I just edited it and posted that little blurb instead.

Sorry for the confusion.

Scott
[/quote]
NOTE: If you need to delete a post, please feel free to contact myself or a Moderator, and we can help you out.









Happy Trails,
Doug


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## Oregon_Camper

PDX_Doug said:


> NOTE: If you need to delete a post, please feel free to contact myself or a Moderator, and we can help you out.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Happy Trails,
> Doug


Was this feature removed when we went through the upgrade or did you and the mods decide it was best to remove it from our hands?


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## Thor

Just cught up the last 3 pages since I lasted posted!!! Jan 30/08 will be one for the history books.

The poll will tell all....... and we need a small bet ......Doug.









Since this all for fun the bet will be...if you agree

The person with the wrong answer(you) will serve the person with the right answer(me) breakfest at a rally (lots of witnesses) including fresh squeeze OJ and a copy of the local paper. If the rally happens to be in Canada, than a Timmy's is apart of the deal.

Handshake?

Thor


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## tdvffjohn

Oregon_Camper said:


> NOTE: If you need to delete a post, please feel free to contact myself or a Moderator, and we can help you out.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Happy Trails,
> Doug


Was this feature removed when we went through the upgrade or did you and the mods decide it was best to remove it from our hands?
[/quote]

It was more about accountability. Some posts were being posted to stir the pot and then deleted. If something needs to be deleted, you can ask Admin or a mod to do it.

John


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## PDX_Doug

Thor said:


> Just cught up the last 3 pages since I lasted posted!!! Jan 30/08 will be one for the history books.
> 
> The poll will tell all....... and we need a small bet ......Doug.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Since this all for fun the bet will be...if you agree
> 
> The person with the wrong answer(you) will serve the person with the right answer(me) breakfest at a rally (lots of witnesses) including fresh squeeze OJ and a copy of the local paper. If the rally happens to be in Canada, than a Timmy's is apart of the deal.
> 
> Handshake?
> 
> Thor


You're on Thor!








And just so you at least get the breakfast part right, I like my bacon just soft of the crispy side.









Happy Trails,
Doug

P.S.: The French Maid outfit is one-size-fits-all, so I'm sure you will have no problem getting into it.


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## Oregon_Camper

you guys really know how to bet large.


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## Thor

PDX_Doug said:


> Just cught up the last 3 pages since I lasted posted!!! Jan 30/08 will be one for the history books.
> 
> The poll will tell all....... and we need a small bet ......Doug.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Since this all for fun the bet will be...if you agree
> 
> The person with the wrong answer(you) will serve the person with the right answer(me) breakfest at a rally (lots of witnesses) including fresh squeeze OJ and a copy of the local paper. If the rally happens to be in Canada, than a Timmy's is apart of the deal.
> 
> Handshake?
> 
> Thor


You're on Thor!








And just so you at least get the breakfast part right, I like my bacon just soft of the crispy side.









Happy Trails,
Doug

P.S.: The French Maid outfit is one-size-fits-all, so I'm sure you will have no problem getting into it.








[/quote]

LMAO

I do not care who you are...that there is funny









Thor


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## Doxie-Doglover-Too

Thor said:


> Just cught up the last 3 pages since I lasted posted!!! Jan 30/08 will be one for the history books.
> 
> The poll will tell all....... and we need a small bet ......Doug.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Since this all for fun the bet will be...if you agree
> 
> The person with the wrong answer(you) will serve the person with the right answer(me) breakfest at a rally (lots of witnesses) including fresh squeeze OJ and a copy of the local paper. If the rally happens to be in Canada, than a Timmy's is apart of the deal.
> 
> Handshake?
> 
> Thor


You're on Thor!








And just so you at least get the breakfast part right, I like my bacon just soft of the crispy side.









Happy Trails,
Doug

P.S.: The French Maid outfit is one-size-fits-all, so I'm sure you will have no problem getting into it.








[/quote]

LMAO

I do not care who you are...that there is funny









Thor
[/quote]

MaeJae, where are you? Time for some of your fancy photoshop work!


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## PDX_Doug

Man... It's too quiet around here!
Is everybody that burned out on Outbacking?

Anyway, it's been awhile - and we've had a lot of new members join since we, um, discussed this one. So...
Time to bring out the BIG GUNS!

*The Great Conveyor Belt Thread Returns!!!*​
May the best French Maid (I'm still waiting, Thor







) win!

Happy Trails,
Doug


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## raynardo

How much wood would a wood chuck chuck if a wood chuck could chuck wood?

_ -> Please show all your work. _


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## PDX_Doug

raynardo said:


> How much wood would a wood chuck chuck if a wood chuck could chuck wood?
> 
> Please show all your work.


Are we talking Oak, or Southern Yellow Pine?


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## Doxie-Doglover-Too

Stop! Stop! Coffee is all over keyboard...again !
















Doug, I can't believe you "resurrected" the conveyor belt!









The only thing I had more fun reading was the remodel of Wolfwood! Good times!


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## sunnybrook29

It will not fly , no movement over wings no lift! An airplane anchored in a hurricane will have airflow over wings and will lift. The engines have nothing to do with it, it is the airflow over the wings.


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## wolfwood

*NOOOOOOOOOOOOOOOOOOOOOOOO !!!!!!!!!!!*
























*RUN AWAY!!!!! RUN AWAY!!!!!*


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## BoaterDan

I'll know I oficially have way too much time on my hands if I ever reply to this argument again.

By the way, of course the plane flies.

Dammit, that slipped out!


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## Doxie-Doglover-Too

BoaterDan said:


> I'll know I oficially have way too much time on my hands if I ever reply to this argument again.
> 
> By the way, of course the plane flies.
> 
> Dammit, that slipped out!


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## Moosegut

BoaterDan said:


> I'll know I oficially have way too much time on my hands if I ever reply to this argument again.
> 
> By the way, of course the plane flies.
> 
> Dammit, that slipped out!










When I saw that Doug brought this up a while ago, I had the exact same feelings - I just didn't post them. But, since YOU have, I agree with everything you said.


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