A 2.0-kg stone is tied to a 0.50-m long string and swung around a circle at a constant angular velocity of 12 rad/s. The net torque on the stone about the center of the circle is:
A) 0
B) 6.0 N. m
C) 12 N . m
D) 72 N .m
E) 140 N . m

Question

Quizplus · Accepted Answer

Since the stone is moving at a constant angular velocity, there is no change in rotational motion and therefore no net torque acting on the stone. In other words, the centripetal force required to keep the stone moving in a circle is equal and opposite to the tension force in the string, resulting in a net torque of zero.

A 20-Kg Stone Is Tied to a 0