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Grade
Level: K - 6
Concepts:
- Potential energy is the energy of height or position. The higher the object, the greater its potential energy.
- In any transformation of energy, some of the energy becomes unavailable for future use.
Materials:
Ball
Tape
Measuring tape or yardstick
Roll of paper 1 meter long
Felt tip pen
Procedure:
1. Starting at the floor, stretch the paper vertically against the wall. Attach it to the wall with tape.
2. Draw lines across the paper to mark 1/2 meter, 3/4 meter, and 1 meter above the floor.
3. Hold the ball in front of the 1/2 meter mark and drop (don't throw) it. Watch very carefully as the ball bounces. Mark the height of the bounce on the paper.
4. Measure the height of the bounce and record it on the chart.
5. Repeat directions 3 & 4 two more times. Record your results.
6. Do the experiments again, starting at the 3/4 meter mark and then again at the 1 meter mark. Remember to mark the bounce heights and record your measurements on the chart.
Follow-Up Discussion:
When you lift the ball, you give it POTENTIAL energy. The amount of potential energy depends partly on the height of the ball. The higher you lift it, the more potential energy the ball has.
When you drop the ball, the potential energy is changed into KINETIC energy. As the falling ball rubs against the air, some of the energy is changed into heat. Some energy changes into sound when the ball hits the floor. Because some energy becomes unusable when it changes from one form to another, the ball will never have enough energy to bounce back up to its starting height. You can't ever get as much energy out of a transformation as you put into it.
How high a ball bounces depends on what it is made of. Some of the energy is used to squash the ball out of shape as it hits the floor. If the ball is very bouncy, it quickly returns to its original shape, releasing most of the energy to bounce back up. If the ball stays squashed, the energy can't help to bounce it back again.
The "bounciness" of a ball is called ELASTICITY. Which has more elasticity, a ball made of clay or one made of rubber? What happens to the energy as each one bounces?
Try dropping the ball on different surfaces (wood, carpet, a tennis racket, sand, metal, etc.). How does the surface affect the ball's bounce?
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