A flywheel is a
rotating mechanical device that is used to store rotational energy.
Flywheels have an inertia called the moment of inertia and thus
resist changes in rotational speed. The amount of energy stored in
a flywheel is proportional to the square of its rotational speed.
Energy is transferred to a flywheel by the application of a torque
to it, thereby increasing its rotational speed, and hence its
stored energy. Conversely, a flywheel releases stored energy by
applying torque to a mechanical load, thereby decreasing the
flywheel's rotational speed.
