Rotational Kinematics with Constant Angular Acceleration: a 1

Essay

Rotational kinematics with constant angular acceleration: A 1.15-kg grinding wheel 22.0 cm in diameter is spinning counterclockwise at a rate of 20.0 revolutions per second. When the power to the grinder is turned off, the grinding wheel slows with constant angular acceleration and takes 80.0 s to come to a rest.
(a) What was the angular acceleration (in rad/s²) of the grinding wheel as it came to rest if we take a counterclockwise rotation as positive?
(b) How many revolutions did the wheel make during the time it was coming to rest?