How is energy transferred from the bicycle wheel?

[Michio Cuckoo]

https://www.youtube.com/watch?v=V3UsrfHa4MQ

So check out the above video.

When the man flips the bicycle wheel over, the turntable he is sitting on starts to rotate. What I don't understand is, how is energy transferred from the bicycle wheel to the turntable?

 

[A.T.]

What I don't understand is, how is energy transferred from the bicycle wheel to the turntable?

Energy isn't transferred from the bicycle wheel to the turntable. Just angular momentum.

 

[Michio Cuckoo]

Energy isn't transferred from the bicycle wheel to the turntable. Just angular momentum.

But where does the turntable get the energy to rotate?

 

[A.T.]

But where does the turntable get the energy to rotate?

From the muscles of the man.

 

[HallsofIvy]

In order to turn the wheel through a right angle, the man must apply force to ends of of the axle. You can trace trace the reaction force through the man's muscles and skeleton to his feet braced on the turn table (obviously, if he were standing on frictionless ice or in space, the motion would be different.)

 

[A.T.]

In order to turn the wheel through a right angle, the man must apply force to ends of of the axle. You can trace trace the reaction force through the man's muscles and skeleton to his feet braced on the turn table

Yes, the forces (or rather torques) are transferring angular momentum from the wheel to the turn table. But there is no energy transferred from the wheel to the turn table.

(obviously, if he were standing on frictionless ice or in space, the motion would be different.)

On ice it would be quite similar to the turn table.

 

[Michio Cuckoo]

In order to turn the wheel through a right angle, the man must apply force to ends of of the axle. You can trace trace the reaction force through the man's muscles and skeleton to his feet braced on the turn table (obviously, if he were standing on frictionless ice or in space, the motion would be different.)

quite a sneaky transfer of energy. Thanks for explaining.

 

[haruspex]

So what happens if he flips the wheel back again? Presumably the man has to work just as hard, but now the turntable stops. Where has the energy gone?