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Skater Rate of Rotation

  1. Nov 15, 2009 #1
    1. The problem statement, all variables and given/known data

    A figure skater is spinning at a rate of 2 rev/s with her arms outstretched. She then draws her arms in to her chest, reducing her rotational inertia to 61% of its original value. What is her new rate of rotation?



    2. Relevant equations

    ?



    3. The attempt at a solution

    w/2 = 1/sqrt(0.61)
    w = 2.56 rev/s

    This isn't correct according to the website, can someobody help me with a better equation and how to solve this one?

    Thanks!
     
  2. jcsd
  3. Nov 15, 2009 #2

    Delphi51

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    Homework Helper

    angular momentum before = angular momentum after
     
  4. Nov 15, 2009 #3
    I still don't really understand
     
  5. Nov 15, 2009 #4

    Delphi51

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    Homework Helper

    Angular momentum is conserved; it stays the same unless there is an external torque. So
    angular momentum before = angular momentum after

    You need to write the formula for angular momentum on both sides. Fill in the quantities you know and solve for the one you want to find.
     
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