A 40-kg boy is standing on the edge of a stationary 30-kg circular platform that is free to rotate.The boy tries to walk around the platform in a counterclockwise direction.As he does:
A)the platform doesn't rotate.
B)the platform rotates in a clockwise direction just fast enough so that the boy remains stationary relative to the ground.
C)the platform rotates in a clockwise direction while the boy goes around in a counterclockwise direction relative to the ground.
D)both go around with equal angular velocities but in opposite directions.

Question

Quizplus · Accepted Answer

According to Newton's Third Law, every action has an equal and opposite reaction. When the boy walks in a counterclockwise direction, he exerts a force on the platform in the clockwise direction. The platform reacts by rotating in the opposite direction to conserve angular momentum. Therefore, the platform will rotate in a clockwise direction while the boy goes around in a counterclockwise direction relative to the ground.

A 40-Kg Boy Is Standing on the Edge of a Stationary