A disk starts from rest and rotates around a fixed axis, subject to a constant net torque.The work done by the torque during the second 5 s is ______ as the work done during the first 5 s.
A)the same
B)half as much
C)twice as much
D)three times as much
E)four times as much

Question

Quizplus · Accepted Answer

The work done by the torque is related to the change in kinetic energy, which depends on the square of the angular velocity. Since the disk starts from rest and the torque is constant, the angular velocity increases linearly with time. Therefore, the kinetic energy, and hence the work done, increases with the square of the time. Thus, the work done in the second 5 seconds is three times the work done in the first 5 seconds.

A Disk Starts from Rest and Rotates Around a Fixed