A Silly Video

[Keith Lane]

But it raises an interesting question.
Just why does it do what it does?

http://www.wimp.com/underruler/

 

[vontresc]

But it raises an interesting question.
Just why does it do what it does?

http://www.wimp.com/underruler/

One word.... Treadmill!

 

[Capt. Geoffrey Thorpe]

But it raises an interesting question.
Just why does it do what it does?

http://www.wimp.com/underruler/

The difference in size between the rim of the spools and the center.

 

[Keith Lane]

The difference in size between the rim of the spools and the center.

I'm in agreement here. The white coated wizard upstairs from me is spouting differential friction coefficients. I don't see no steenkin' slippage, so I don't see how friction comes into play. I'd bet if the center wheel was small and the two bottom ones were big, it'd behave differently.

 

[steingar]

People have been using pulleys for a rather long time.

 

[Capt. Geoffrey Thorpe]

The difference in size between the rim of the spools and the center.

Nope, I was wrong.

If you were to push the cart itself one inch to the right, the top of the center wheel would move less than one inch because the center wheel turns "backwards" - that should be easy to visualize. Turing it around, If you move the top of the center wheel one inch, the cart has to move more than one inch (assuming nothing slips) to "make up" for the retrograde motion of the center wheel.