A rock, tied at the end of a rope, is swirled at a constant speed in a vertical circle. The net work done on the rock
A) is positive.
B) is zero.
C) is negative.
D) changes from positive to negative and back as the velocity of the rock changes its direction.
E) depends on the weight of the rock.

Question

Quizplus · Accepted Answer

The net work done on the rock is zero because the direction of the force (tension in the rope) is always perpendicular to the displacement of the rock at any point in the circle, meaning no work is done by the centripetal force. Additionally, since the speed is constant, kinetic energy does not change, indicating no net work is done on the system.

A Rock, Tied at the End of a Rope, Is