An ice skater spins on nearly frictionless ice with her arms extended
PHYSICS · Single correct · CBSE · Physics · System of Particles and Rotational Motion · System of Particles and Rotational Motion
Problem
An ice skater spins on nearly frictionless ice with her arms extended. She then pulls her arms close to her body and her spin rate increases. Which statement best explains the increase in her angular speed, assuming negligible external torques?
(a) By decreasing her radius, the inward centripetal force produces a net torque that speeds her up.
(b) Her moment of inertia decreases, so her angular momentum decreases and her angular speed must increase to conserve energy.
(c) Her moment of inertia decreases, so to keep angular momentum constant her angular speed must increase.
(d) Muscular work adds angular momentum to her system, so her angular speed increases even though her moment of inertia falls.