# Brain Teaser #2



## 2500Ram (Oct 30, 2005)

OK, Here is another one: If a bulldozer is moving at a speed of 5mph the top of the track is moving at 10mph. How fast is the track on the bottom going?

Have fun

Bill


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## CamperAndy (Aug 26, 2004)

2500Ram said:


> OK, Here is another one: If a bulldozer is moving at a speed of 5mph the top of the track is moving at 10mph. How fast is the track on the bottom going?
> 
> Have fun
> 
> ...


The assumption that the top of the track is moving at 10 mph is wrong. It is moving at the speed of the bulldozer and if the dozer is going 5 mph then the top and bottom of the track is also going 5 mph.


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## 2500Ram (Oct 30, 2005)

CamperAndy said:


> 2500Ram said:
> 
> 
> > OK, Here is another one: If a bulldozer is moving at a speed of 5mph the top of the track is moving at 10mph. How fast is the track on the bottom going?
> ...


Wrong


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## CamperAndy (Aug 26, 2004)

Okay I was back on the convoy belt.

When on solid ground the bottom of the track is at rest but the track moving on the top is still just doing the speed of the tractor.


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## PDX_Doug (Nov 16, 2004)

Actually, the bottom of the track isn't moving at all.









Happy Trails,
Doug


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## 2500Ram (Oct 30, 2005)

CamperAndy said:


> Okay I was back on the convoy belt.
> 
> When on solid ground the bottom of the track is at rest but the top track is still just doing the speed of the tractor.
> [snapback]65935[/snapback]​


Correct but still wrong, the bottom is at rest like you said but the top is moving at 10 MPH.


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## nascarcamper (Jan 27, 2005)

Excuse me if this gets posted twice but my computer had a hiccup when replying. Are you trying to keep us up all night? My thinking would be the bottom track would have to be moving at the speed of the bull dozer. The top one could be going faster if the gear is larger or smaller on one end or if it's one with three gears. It think it goes something like for every action there is an equal but opposite reaction? This is deep. By the way is the bulldozer in soft sand spinning it's tracks?


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## PDX_Doug (Nov 16, 2004)

OK, let's take a stab at the top track...

It is moving the 5MPH that the dozer is moving relative to the ground + another 5MPH so that the track in back can catch up with the front of the track loop. Thus... 10MPH.

Happy Trails,
Doug


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## 2500Ram (Oct 30, 2005)

Think of standing next to a bulldozer, the bottom track is not moving from where you are standing correct, so therefor the the track is really moving 10mph on top even though the dozer is only going 5mph, only half of the track is moving.

Good night, I'll be back tomorrow with more I hope.

Bill.


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## Paul_in_Ohio (Sep 29, 2004)

The Top part of the track is moving at 10 and the bottom part is moving at 0, as long as the tractor isn't spinning its tracks.

If you have microwave with a carosel with a clear plate and the little "lazy susan" type drive mechanizim, you can see it in action. As the unit runs, the plate turns faster than the "lazy susan" by a factor of 2.


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## sircarryalot (Jun 23, 2005)

2500Ram said:


> OK, Here is another one: If a bulldozer is moving at a speed of 5mph the top of the track is moving at 10mph. How fast is the track on the bottom going?
> 
> Have fun
> 
> ...


Zero


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