A boy stands on a merry-go-round platform at rest. When the boy starts walking tangentially along the edge of the platform in a clockwise direction, the platform will
A) start rotating in a clockwise direction.
B) stay at rest until an external force acts on it.
C) stay at rest until an external torque acts on it.
D) start rotating in a counterclockwise direction.

Question

Quizplus · Accepted Answer

When the boy walks tangentially in a clockwise direction, by the principle of conservation of angular momentum, the platform will start rotating in the opposite direction, which is counterclockwise, to conserve the total angular momentum of the system.

A Boy Stands on a Merry-Go-Round Platform at Rest