A 30-kg child sitting 5.0 m from the center of a merry-go-round has a constant speed of 5.0 m/s. While she remains seated in the same spot and travels in a circle, the work the seat performs on her in one complete rotation is
A) 0 J.
B) 150 J.
C) 1 500 J.
D) 4 700 J.
E) 46 000 J.

Question

Quizplus · Accepted Answer

The work done by a force is given by the formula W = Fd cos θ, where F is the magnitude of the force, d is the distance through which the object moves, and θ is the angle between the force and the direction of motion. In this case, the force is the normal force of the seat on the child, which is always perpendicular to the direction of motion, so θ = 90° and cos θ = 0. Therefore, the work done by the seat on the child is zero, regardless of the distance or speed traveled.

A 30-Kg Child Sitting 5