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Conditions for Pulley

  1. Jun 22, 2013 #1
    When we say "pulley is frictionless", do we mean its groove where the string moves or its axle or both?
     
  2. jcsd
  3. Jun 22, 2013 #2

    mfb

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    The axle - but if you can neglect kinetic energy of the wheel, a frictionless groove gives the same result.
     
  4. Jun 22, 2013 #3
    How? How does it give the same result as an axle which has friction, if we neglect KE of the wheel?
     
  5. Jun 22, 2013 #4

    mfb

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    The pulley will not dissipate any energy, and the magnitude of force is the same everywhere in the rope.
    That is true for every ideal, frictionless pulley, it does not even depend on the details how you design the pulley.
     
  6. Jun 22, 2013 #5

    haruspex

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    That's not what mfb wrote. mfb said that (frictionless axle with massless wheel) gives the same result (i.e. no role in the equations) as frictionless groove.
     
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