Bouncing ball energy lab
01 // Question
How does the type of ball change the percent of drop height it bounces back to?
A testable question names one thing you change (ball type) and one thing you measure (bounce height).
02 // Variables
Independent
Type of ball- Tennis ball
- Basketball
- Ping pong ball
- Rubber bouncy ball
Dependent
Bounce height as a percent of drop height- Bounce height in cm
- Percent of drop height returned
03 // Hypothesis
IF a ball with more elastic material is dropped from a fixed height, THEN it will bounce back to a greater percent of that height, BECAUSE a more elastic ball loses less energy to heat and deformation on impact, returning more of its energy as upward motion.
04 // Procedure
1. Mark the drop height
Set a fixed drop height, such as 100 cm, measured against a wall or board with height markings.
2. Release each ball
Hold each ball at the marked height and drop it straight down without throwing it.
3. Watch the bounce
Watch closely where the ball reaches its highest point on the first bounce.
4. Measure the bounce height
Record the height of that first bounce for each ball, repeating each ball 3 times.
5. Calculate the percent
Divide each average bounce height by the drop height and multiply by 100.
05 // Data table
| Ball type | Trial 1 (cm) | Trial 2 (cm) | Trial 3 (cm) | Average % of drop height |
|---|---|---|---|---|
| Tennis ball | ____ | ____ | ____ | ____ |
| Basketball | ____ | ____ | ____ | ____ |
| Ping pong ball | ____ | ____ | ____ | ____ |
| Rubber bouncy ball | ____ | ____ | ____ | ____ |
Formula Bounce % = (bounce height ÷ drop height) × 100
06 // What to expect
A rubber bouncy ball usually returns the highest percent of its drop height, since its material is built to deform and spring back with very little energy lost, while a ball like a basketball or tennis ball loses more energy to heat, sound and deformation on each bounce.
No ball returns 100% of its drop height, because some energy always converts to other forms — heat inside the ball, sound from the impact, and small movements of the floor — on every real-world bounce.
07 // Lab notes
- Drop each ball from the exact same height and release it the same way — a small toss instead of a drop adds extra energy that isn't part of the test.
- Test on the same hard, flat floor for every ball — carpet or an uneven surface absorbs more energy and skews the comparison.
- Watching the exact top of a fast bounce takes practice — recording in slow motion on a phone makes the height easier to read accurately.
08 // Remember
A bouncing ball never gets all its energy back. Some always leaks out as heat and sound — the better the bounce, the less it leaks.
09 // Questions people ask
Why do some balls bounce higher than others from the same drop height?
How high a ball bounces depends on how much of its energy is lost to heat, sound, and deformation on impact versus how much converts back into upward motion. A more elastic ball, like a rubber bouncy ball, loses very little energy on impact, while a less elastic ball loses much more, resulting in a lower bounce.
Why doesn't any ball bounce back to exactly the height it was dropped from?
The law of conservation of energy says energy can't be destroyed, but it can change form. On every bounce, some of the ball's energy converts into heat inside the material, sound from the impact, and tiny vibrations in the floor — none of that energy converts back into height, so the bounce is always a little lower than the drop.
What is the dependent variable in the bouncing ball experiment?
It's typically the bounce height, often expressed as a percent of the original drop height so that balls dropped from different heights (or by different people, in different trials) can still be fairly compared.