A passenger bus in Zurich, Switzerland, derived its motive power from the energy stored in a large flywheel. The wheel was brought up to speed periodically, when the bus stopped at a station, by an electric motor, which could then be attached to the electric power lines. The flywheel was a solid cylinder with mass 1000 kg and diameter 1.80 m; its top angular speed was 3000 rev/min.
(a) At this angular speed, what is the kinetic energy of the flywheel?
(b) If the average power required operating the bus is 1.86 X 104 W, how long could it operate between stops?