This classic device is used to demonstrate the conservation of mechanical energy. When the wheel is rotated by hand to the top and released, its potential energy turns into kinetic energy (rotation) as it falls. After the wheel reaches its bottom position, the kinetic energy changes back to potential energy when it moves up again. This process continues until the total energy is lost because of friction. Dimensions, 18 × 2 × 5"; wt, 5.6 lb. Instructions included.