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A rotational problem

  1. Dec 8, 2008 #1
    1. The problem statement, all variables and given/known data
    A stick of length L and mass M lies on a frictionless horizontal surface on which it is free to move in anyway.
    A ball of mass m moving with speed v collides elastically with the stick at a distance d below its centre.
    (a) Which quantities are conserved in this collision?
    (b) What must be the mass of the ball so that it remains at rest immediately after collision?

    2. Relevant equations

    3. The attempt at a solution
    Here if we conserve linear momentum,
    we get mv=Mv1 (As the ball remains at rest.)
    But I don't think this is right because if we conserve angular momentum, then we get something else, and if we conserve kinetic energy, then we get something else.
    So fow do i go about this question?
  2. jcsd
  3. Dec 9, 2008 #2


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    Science Advisor
    Homework Helper

    Hi iitjee10! :smile:

    i] in any collision (with no external forces), both momentum and angular momentum are always conserved

    ii] what does "elastically" mean?
  4. Dec 9, 2008 #3


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    Gold Member

    It means they collide with no loss of kinetic energy. :wink:
  5. Dec 10, 2008 #4
    elastically means coefficient of restitution is 1
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