Useful for demonstrating momentum, conservation of energy and torque, this apparatus is basically a large metal flywheel suspended by two strong cords in a metal frame. The cords are wound around the shaft of the wheel which is then released. The wheel will unwind as it falls but will wind itself back up as the momentum carries it upward in the opposite direction. This oscillation process will continue for several rotations before gradually coming to a stop as the wheel slowly loses momentum and travels less each time.