Energy on the Move

Purpose: To understand the difference between potential and kinetic energy

Background

Potential energy is energy that an object has due to its position or condition. For example, a stretched rubber band has potential energy because of its condition. The amount of gravitational potential energy stored in an object depends on two factors: how much mass the object has and how high above the Earth it is positioned. Kinetic energy is the energy an object has because of its motion.

Materials

• golf ball
• baseball
• ping-pong ball
• basketball
• tennis ball
• science journal
• meter stick

Procedure

1. On a flat surface, hold a meter stick vertically so that one end is touching the surface.
2. Choose one of the balls and hold it in your hand so that the ball’s bottom is even with the top of the meter stick.
3. Do you think the ball has energy? If so, what kind?
4. Drop the ball and count the number of times it bounces before coming to a stop. Record the results in your science journal.
5. Describe what the ball did as it was dropped. Be sure to include energy terms in your description.
6. Repeat with each of the other balls.
7. Create a chart or graph to display your results.
8. Compare your results with other groups and as a class.

Conclusion

1. As you held the ball, what type of energy did it possess? Explain.
2. Using energy terms, explain what happened as the ball fell and then bounced back up again.
3. List examples of potential and kinetic energy that you see in everyday life

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Answer Key

1. The ball had potential energy or stored energy. It gained potential energy when it was lifted.
2. As you let go of the ball, the potential energy started to change into the energy of motion or kinetic energy. The energy that was stored in the ball is released. When the ball hits the floor, all the potential energy changes into kinetic energy; then, when it bounces up again, the kinetic energy changes back into potential energy.
3. Answers will vary, but might include a parked car, a batter holding a bat, a rock at the top of a cliff, a moving car, a rubber band snapping back into position, and so on.