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Angular momentum of puck question

  1. Mar 1, 2009 #1
    1. The problem statement, all variables and given/known data
    The figure represents a small, flat puck with mass m = 2.41 kg sliding on a frictionless, horizontal surface. It is held in a circular orbit about a fixed axis by a rod with negligible mass and length R = 1.16 m, pivoted at one end. Initially, the puck has a speed of v = 4.72 m/s. A 1.50 kg ball of putty is dropped vertically onto the center of the puck from a small distance above it and immediately sticks to the puck.
    a.what is the new period of rotation?
    b.Is angular momentum of the puck-putty system about the axis of rotation conserved in this process? choices:
    Angular momentum of the puck-putty system is conserved.
    Angular momentum of the puck-putty system in NOT conserved.
    The pivot exerts a definite torque.
    The pivot exerts NO torque.
    c.Which statements are true regarding the conservation of mechanical energy of the system in the process?
    Some mechanical energy is converted into internal energy.
    The collision is perfectly elastic.
    The mechanical energy is conserved.
    The collision is perfectly inelastic.
    2. Relevant equations

    3. The attempt at a solution
    so i dont know how to start part a..any suggestions?
  2. jcsd
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