A car is designed to get its energy from a rotating flywheel with a radius of 2.25 m and a mass of 525 kg. The flywheel can be considered as a uniform thin cylinder. Before a trip, the flywheel is attached to an electric motor, which brings the flywheel's rotational speed up to 5000 rev/min.
a) What is the kinetic energy stored in the flywheel?
b) If the flywheel is to supply energy to the car as would a 20-hp motor, find the length of time the car could run before the flywheel would have to be brought back up to speed.