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How is energy transferred from the bicycle wheel?

  1. Jun 11, 2012 #1
    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?
     
    Last edited: Jun 11, 2012
  2. jcsd
  3. Jun 11, 2012 #2

    A.T.

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    Energy isn't transferred from the bicycle wheel to the turntable. Just angular momentum.
     
    Last edited: Jun 11, 2012
  4. Jun 11, 2012 #3
    But where does the turntable get the energy to rotate?
     
  5. Jun 11, 2012 #4

    A.T.

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    From the muscles of the man.
     
  6. Jun 11, 2012 #5

    HallsofIvy

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    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.)
     
  7. Jun 11, 2012 #6

    A.T.

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    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.
    On ice it would be quite similar to the turn table.
     
  8. Jun 13, 2012 #7
    quite a sneaky transfer of energy. Thanks for explaining.
     
  9. Jun 13, 2012 #8

    haruspex

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    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?
     
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