A solid uniform disk of radius 0.30m and mass 4.0kg is free to rotate about its central axis. The disk starts from rest. An electric motor applies a constant 6.0N⋅m torque to the disk for 3.5s. After the motor is switched off, a small frictional torque of 0.75N⋅m opposite the direction of rotation slows the disk to a stop.
(a) Calculate the angular impulse delivered to the disk by the motor.
(b) Determine the disk’s angular speed immediately after the motor shuts off. Include appropriate units.
(c) How much time elapses from the moment the motor turns off until the disk comes to rest? Show your reasoning.