An ice skater of mass is standing on frictionless ice
PHYSICS · Multi-part · CBSE · Physics · System of Particles and Rotational Motion · System of Particles and Rotational Motion
Problem
An ice skater of mass 60kg is standing on frictionless ice, rotating about a vertical axis through her body with an initial angular speed of 2.0rads−1. With arms fully extended, her moment of inertia about the axis is Ii=3.0kgm2. She then pulls her arms inward, reducing her moment of inertia to If=1.2kgm2. Air resistance is negligible, and the ice provides no horizontal forces that exert a torque about the rotation axis.
(a) Determine the skater’s angular speed immediately after she has pulled in her arms.
(b) Calculate the percentage change in the skater’s rotational kinetic energy as a result of pulling in her arms.
(c) Briefly explain where the additional or missing mechanical energy calculated in part (b) originates or goes, making explicit reference to forces or work done within the skater’s body.