Maxwell's wheel and the conservation of energy

  • #1
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We experimented with the Maxwell's wheel today and at the end we were asked about why does this apparatus stop since there is conservation of energy.
I did some research and apparently there is a type of friction called "rolling friction", wikipedia defines it as "the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface."
So is, in this case, the rope considered as the surface?
 

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  • #2
berkeman
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We experimented with the Maxwell's wheel today and at the end we were asked about why does this apparatus stop since there is conservation of energy.
I did some research and apparently there is a type of friction called "rolling friction", wikipedia defines it as "the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface."
So is, in this case, the rope considered as the surface?
What properties of a tire and road surface contribute to rolling resistance? And what properties of the wheel axle and string contribute to any spinning resistance in the Maxwell's Wheel experiment?

https://cdn.shopify.com/s/files/1/1342/5013/products/8807741_1_large.jpg?v=1472087648

8807741_1_large.jpg
 

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  • #3
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What properties of a tire and road surface contribute to rolling resistance? And what properties of the wheel axle and string contribute to any spinning resistance in the Maxwell's Wheel experiment?

https://cdn.shopify.com/s/files/1/1342/5013/products/8807741_1_large.jpg?v=1472087648

View attachment 231263
After some research, the resistance is due to either a deformation in the object, the surface or both.
I guess it's the same for the axle and the strings, either one of them or both aren't totally rigid which causes some kind of "braking" each time until all movement stops.
 
  • #4
berkeman
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Yeah, in the case of Maxwell's Wheel, the axle is pretty hard metal, so it won't deform. But how much energy does it take to keep wrapping and unwrapping the string around that rigid axle? :smile:
 
  • #5
CWatters
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You should also consider other causes of energy loss.
 
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  • #6
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Suppose the strings were attached to spring scales instead of fixed supports.
What would you expect to happen to the scale readings during a cycle?
 
  • #7
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Apparently the loss of energy is due to the non perfect elasticity of the strings
 
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  • #8
CWatters
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I'd be surprised if there was only one way energy was lost.
 
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  • #9
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Apparently the loss of energy is due to the non perfect elasticity of the strings
In my earlier post I implied that use of a spring scales would show discontinuities in the motion.
Kinematics seems to indicate that this is not the case and a scales would be
of little or no use.
As indicated in post #8 other factors must be at work here such as
(work in bending the cords, friction, etc.).
I haven't had the opportunity to observe that apparatus and don't
happen to have a yo-yo.
 

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