# The rate of rotation of a solid disk with a radius of #4 m# and mass of #5 kg# constantly changes from #12 Hz# to #5 Hz#. If the change in rotational frequency occurs over #12 s#, what torque was applied to the disk?

##### 1 Answer

Jul 18, 2016

#### Answer:

#183.3 "N m" clockwise.

#### Explanation:

Although it doesn't say so in the problem, it seems safe to assume that the disk is rotating about an axis passing through its center and normal to it, In this case the moment of inertia about this axis is given by

To calculate the angular momentum we use

Thus the torque is