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A skater spinning with angular speed of 1.5 rad/s draws in her outstretched arms thereby reducing her moment of inertia by a factor a 3.
a) Find her angular speed.
b)What is the ratio of her final angular momentum to her initial angular momentum?
c)Did her mechanical energy change? (Yes but why?)

  • Physics -

    I forgot to add one more part.

    d) Determine the ratio of her final kinetic energy to her initial kinetic energy.

  • Physics -

    I*w stays the same due to the requirement for angular momentum conservation.

    If I is cut in half, w must double.

    KE is (1/2)I*w^2 = (1/2)(I*w)^2/I

    Since I drops by half while I*w is constant, the kinetic energy must also double.

    The extra KE comes from work done by the skater pulling in her arms. There is a lot of centrifugal resistance.

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