When a juggler tosses a bean ball straight upward, the ball slows down until it reaches the top of its path and then speeds up on its way back down. In terms of energy, when the ball is released it has kinetic energy, KE. As it rises during its free-fall phase it slows down, loses kinetic energy, and gains gravitational potential energy, PE. As it starts down, still in free fall, the stored gravitational potential energy is converted back into kinetic energy as the object falls.

If there is no work done by frictional forces, the total energy remains constant. In this experiment, we will see if this is true for the toss of a ball. We will study these energy changes using a Motion Detector.


  • Measure the change in the kinetic and potential energies as a ball moves in free fall.
  • See how the total energy of the ball changes during free fall.