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B Does the gravitational force change for a spinning wheel

  1. Oct 1, 2016 #1
    When a wheel spins does it generate lift or something, the wheel spins so that the torque force is downwards.

    for example you measure the weight of the wheel and then you spin then wheel does anything change?
    The wheel is solid and if their change something does it matter if it is a constant velocity or an acceleration.
     
  2. jcsd
  3. Oct 1, 2016 #2
    No, spinning makes no difference to the mass of the wheel.
    Hence it will accelerate in a gravitational field exactly the same as a non-spinning wheel.
    (Assuming we are considering what happens in a vacuum that is - if air is present then the spinning might create some aerodynamic effects, but still the mass of the wheel won't change)
     
  4. Oct 1, 2016 #3
    if their will be air and the wheel spins fast enough is their cab their be a lift force?
    i know the mass won't change but what about the total downwards force?
     
  5. Oct 1, 2016 #4
    Yes, the wheel could be intentionally designed to generate lift as a result of the rotation .
    Essentially that's what a helicopter rotor does.
    However this doesn't reduce the force of gravity or affect the mass.
    It just produces a counter-force acting in the opposite direction.
     
  6. Oct 1, 2016 #5

    jbriggs444

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    For a symmetrical wheel in a symmetric atmosphere, the symmetry guarantees that there can be neither upward nor downward forces (*). The fact that the rotation [pseudo-]vector points downward is irrelevant. It is purely a matter of convention whether the rotation from a wheel spinning clockwise is seen as pointing toward the viewer or away from the viewer.

    (*) There is a theoretical possibility that the rotation could set up a stable asymmetric circulation, but it would be a 50/50 chance which direction the asymmetry would point.
     
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