If you can find Tinker Toys™, then this may be a fun assignment for your physical science class. Using the construction set and a few other toys, they examine the forces involved when it they are being played with. For each, they determine how potential energy is stored, when kinetic energy is in action, and how energy is transferred. The lesson is long and materials heavy, but if you prepare a kit with the materials, you can use it over and over again to help you teach energy.