At t = 0 s a flywheel is rotating at 25 rpm. A motor gives it a constant acceleration of 0.8 rad/s2 until it reaches 100 rpm. The motor is then disconnected. How many revolutions are completed at t = 23 s?

Answer 1

The average speed during acceleration is 37.5 rpm.

The time spent accelerating is
(75 rpm)*(2 pi/60 rad/s*rpm)/0.8 rad/s^2= 9.8 seconds = 1.63 min

The number of revolutions turned while accelerating is
37.5*1.63 = 6.12

Add to that the number of revolutions turned after the motor is disconnected. They should tell you if it remains at constant speed after that. Friction will tend to slow it down, and they provide no information on that