Will a ball traveling twice as fast as another ball of the same mass really have four times the kinetic energy? Demonstrate the relationship between speed and kinetic energy by dropping a ball from two different heights onto a bed of soft clay. For the second drop, the ball is traveling twice as fast, and it forms a crater four times as deep, indicating that it has four times the energy-the energy is proportional to the square of the ball's speed. The clay bed is prepared by pressing clay into a mold of two semicircles. After the demonstration, the clay can be removed from the mold and then cut in half along the crater marks to measure and compare the depth of the craters. All the materials are completely reusable. Detailed instructions, historical background information, and student worksheet are provided. Note: the clay must be heated prior to use in order to soften it. A laboratory microwave offers the quickest method, but a ceramic hot plate will work too.