A flywheel is a solid disk that rotates about an axis that is perpendicular to the disk at its center.

A flywheel is a solid disk that rotates about an axis that is perpendicular to the disk at its center. Rotating flywheels provide a means for storing energy in the form of rotational kinetic energy and are being considered as a possible alternative to batteries in electric cars. The gasoline burned in a 461-mile trip in a typical midsize car produces about 3.72 x 10