Final answer:
The unit used to measure angular acceleration is rad/s² (radians per second squared), which indicates how quickly the angular velocity changes over time.
Step-by-step explanation:
The unit used to measure angular acceleration is rad/s² (radians per second squared). This unit measures how quickly the angular velocity of an object is changing over time. An object with a steady increase or decrease in its angular velocity has constant angular acceleration.
For example, if the racket is given an angular acceleration of magnitude 160, it is understood to be 160 rad/s².
As another example, if an object's angular velocity changes from 3 rad/s clockwise to 8 rad/s clockwise in 5 seconds, its angular acceleration can be calculated as the change in angular velocity divided by the time interval, which would yield an angular acceleration of 1 rad/s².
Thus, for a tennis serve, when we refer to an angular acceleration of 160, we are discussing the rate at which the angular velocity of the tennis racket is increasing per second, per second.The unit used to measure angular acceleration is rad/s² (Option D)