Sort the forces as producing a torque of positive, negative, or zero magnitude about the rotational axis identified in part
a. keep in mind that counterclockwise rotations are positive.

Rotational motion with a constant nonzero acceleration is not uncommon in the world around us. for instance, many machines have spinning parts. when the machine is turned on or off, the spinning parts tend to change the rate of their rotation with virtually constant angular acceleration. many introductory  problems in rotational kinematics involve motion of a particle with constant, nonzero angular acceleration.