A catapult is a device used to hurl an object. It uses a simple machine called a lever (the spoon and craft stick), which is attached to a stationary point called a fulcrum (the cardboard tube), to help move a load (the marshmallow). Your catapult is powered by the rubber band. When you pull back on the lever, potential energy is stored in the rubber band. When you let go, the potential energy is transferred to the lever and turned into the energy of motion (or kinetic energy), and the marshmallow is flung forward. Download this "Fetch!" PDF, and build a catapult using a lever, and power it with a rubber band!