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Homework Help: Help with this problem

  1. Jul 1, 2009 #1
    1. The problem statement, all variables and given/known data
    A child with a mass of 40kg is sitting 2m from the center of a merry go round. He moves inward to a point 1.5m from the center. If the merry go round was originally spinning at 30rpm's, how fast is it spinning after the child moves inward?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jul 1, 2009 #2


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    Homework Helper

    Welcome to PF.

    How would you think to approach the problem?
  4. Jul 1, 2009 #3
    I really do not have a clue. i cant seem to find which formula I need to use.
  5. Jul 1, 2009 #4
    What is the initial state?
    What is the final state?
    The preservation of what quantities holds here?
  6. Jul 1, 2009 #5


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    Gold Member

    Hint: No net external torque acts on the system.
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