This unit can be used for a variety of purposes to illustrate energy transfers: it can be used to lift a mass or stretch a bungee cord, and to generate an electrical current when the mass falls again or the bungee cord is released. It can also be turned by hand to generate a current. The motor/generator (6 – 9V) is mounted on a robust metal base, and the gearing of the unit and the sizes of the pulleys have been chosen to enable a variety of qualitative and quantitative experiments to be undertaken.