This classic device is used to demonstrate the conservation of mechanical energy and its conversion from one form to another.  After the wheel is rotated by hand to roll the supporting cords to the top and then released, its potential energy turns into kinetic energy of rotation as it falls.  After the wheel reaches its bottom position, the kinetic energy changes back to potential energy as it rolls the cords up again.  This process continues until all the energy is lost to friction.  All metal construction.  Includes activity guide.