Bouncing Ball: Energy Loss on Impact
1 · Predict
When a ball is dropped and bounces off the floor, does it rebound to the same height it was dropped from, a higher height, or a lower height?
- It rebounds to the same height (no energy is lost).
- It rebounds higher than the drop height.
- It rebounds lower than the drop height (some energy is lost).
2 · Set Up
- Open the Bouncing Ball preset. Note the ball's starting height above the floor and its mass.
- Confirm the height probe is attached to the ball — it reports the ball's height above the floor in meters.
- Run the simulation and let the ball fall and bounce. Pause at the top of the first rebound and record the peak height reached.
3 · Collect Data
| Mass (kg) | Drop Height (m) | Gravitational PE (J) | Rebound Height (1st bounce) (m) |
|---|---|---|---|
| 1 | 1.5 | ||
| 1 | 2 | ||
| 1.5 | 2.5 |
Graph rebound height (y-axis) against drop height (x-axis) for your three trials. Describe the shape of the line.
4 · Analyze
- For each row, divide the rebound height by the drop height. What do you notice about this ratio across your three trials?
- The ball's restitution is 0.8. Square that value and compare it to the ratio you computed above. What relationship do you find?
5 · Extend
- If the height ratio you found stays constant bounce after bounce, predict the peak height of the *second* rebound for your first trial. How many bounces would it take before the peak height drops below 1 cm?
- A real dropped ball also loses a little energy to air resistance and sound on each bounce. Would you expect a real ball's rebound heights to fall off faster or slower than the idealized e² pattern you found here?
The Physics Behind This Experiment
Gravitational Potential Energy
The energy stored in the ball's height above the floor just before release — this is the energy budget available to convert into kinetic energy during the fall and, after the bounce, back into height.
Kinetic Energy
The energy of the ball's motion. Just before impact, essentially all of the drop's PE has converted to KE; the bounce then returns only a fraction of that KE, which is why the rebound falls short of the drop height.