When you stretch a rubber band, potential energy is transferred from you to the rubber band. When the rubber band is released, the potential energy is converted to kinetic energy as it flies through the air. Experiment by stretching the band to different lengths to determine if different amounts of energy are produced. If the band is stretched only a little, it won't fly very far because only a small amount of potential energy is transferred. If the rubber band is stretched to its limit, it flies far because more potential energy has been transferred.
Gravity plays a role in creating kinetic energy. Demonstrate this using a basketball. Have students hold a basketball over their heads. Release the ball. Explain that gravity is pulling the ball towards the Earth, which creates kinetic energy as the ball drops. When the ball hits the ground, the energy is converted back to potential energy. As it bounces, the conversion from potential to kinetic continues. Have students watch the ball continue bouncing and observe how high it bounces each consecutive time.
Create a roll-back toy to demonstrate kinetic and potential energy. Punch a hole in the lid and in the bottom of a plastic bottle. Insert a string through the bottom hole and pull it through the top, leaving some string hanging out. Tie the top end of the string to a rubber band and slip a taped stack of washers over the rubber band as a weight. Insert the rubber band through the lid and slide a toothpick through the band so that the toothpick lies horizontally on the lid. This secures the band in place. Place the lid on the bottle and pull the bottom string until the rubber band comes through the bottom hole. Secure the rubber band in place with another toothpick. When you roll the bottle away from you, the weighted section remains still, while the free ends twist. The further you roll the bottle, the more potential energy it gains as the rubber band twists. When you release the bottle, the energy is converted to kinetic and it rolls back again.
Demonstrate where energy goes by bouncing a tennis ball. Attach a length of paper to the wall and mark four-inch intervals up to six feet along the side. Hold a tennis ball at the two-foot mark and drop it. Record how high it bounced up the paper. Drop the ball from three feet and record how high it bounces. Repeat dropping the ball onr foot higher until you reach six feet. The tennis ball has potential energy when it is held. When the ball is released, it has kinetic energy. When the ball is raised, energy is transferred from you to the ball. The higher you hold the ball, the greater the potential energy it has and the more kinetic energy results when you release it.