Question

Please provide me a step by step analysis of how i would solve this problem?

1. An ice skater is holding out a 18 kg mass in her hand and is spinning with a linear velocity of 4.0 m/s with her arms extended 0.80 meters long in relation to the center of her body. If she pulls her arm in, still holding the 18 kg mass, so that she extends her arms to 0.20 meters, what will the Velocity of the mass be?

Thank you!!

Answer 1

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Note: There are a couple assumptions that I have assumed, which allowed me to apply conservation of angular momentum:

1. Ice skater's moment of inertia is negligible relative to the 18kg mass she is holding. The reasons is that the 18kg mass is relatively at larger distance from the axis of rotation than the distance in which the skater is confined. Another reason is no specification (like mass, her average width) of the skater is given in the question.

2. There is no interaction(friction) of the skater with the ice on which she is rotating. This do not allow the angular momentum to be passed to the ice(and therefore earth) which would of course complicate the application of conservation of angular momentum.