All lessons › Challenge: Energy detectives › Lesson 3
Australian primary science · Years 5–6 (challenge) · Lesson 3 of 3
The bouncing ball challenge
Inquiry question: Why does a bouncing ball never bounce back as high as it was dropped from?
Check practical materials
Observing and testing
What students learn
A dropped ball transforms gravitational potential energy to kinetic energy, then squashes and stores elastic energy, then springs back. Some energy is transferred to heat and sound every bounce, so each bounce is lower.
Success criteria
- I can measure bounce heights accurately and repeat my measurements.
- I can find the pattern in bounce heights.
- I can explain the pattern using energy transfers, and evaluate my method.
Preparation and materials
Before this lesson: Students can describe gravitational potential and kinetic energy and how friction transfers energy to heat (lessons 1 and 2).
- Tennis balls — 13 (1 per pair)
- A second kind of ball: ping-pong balls, rubber balls or basketballs — 13 (or share between pairs)
- Metre rulers or tape measures — 13
- Masking tape (to fix rulers to a wall or table leg) — 1 roll
- A hard floor (concrete, wood or vinyl) — 1 area
Teacher setup
- Tape metre rulers upright against walls or table legs around the room, zero at the floor.
- Practise one drop yourself: it is easier to see the bounce height if you crouch to eye level.
- If phones or iPads are allowed, slow-motion video makes reading the bounce height much more accurate.
Safety and adaptations
- Drop balls; don’t throw them.
- Keep clear space around each drop zone so no one trips.
- Basketballs are heavy: drop them only from 1 metre, away from feet.
Review your school policies and curriculum requirements before teaching.
How to investigate
The lesson sequence should leave pupils with evidence to interpret, not only an activity to finish.
- Write a hypothesis about drop height and bounce height, using energy in the ‘because’.
- Drop a tennis ball from 100 cm. Record the first, second and third bounce heights (use slow-motion video if allowed). Repeat three times.
- Drop from 50 cm and 75 cm too, and record the first bounce each time.
- Test the second kind of ball from 100 cm.
- Find the pattern: about what fraction of the height is kept each bounce? Compare your results with the supplied data.
- Evaluate: what made your measurements less accurate, and how could you improve them?
Teacher modelling prompt
Drop a tennis ball from 1 metre beside a taped ruler. Think aloud: “It bounced to about 55 cm. My eye was above the ball, so I may have read it wrong. If I crouch so my eye is level with the top of the bounce, I’ll be more accurate. I’ll do it three times and find the average.” Write the hypothesis frame: “If we drop the ball from higher, then…, because…”.
Record and explain evidence
Recording question: Why does a bouncing ball never bounce back as high as it was dropped from?
| Ball | Drop height (cm) | 1st bounce (cm) | 2nd bounce (cm) | Fraction of height kept |
|---|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
Which claim explains why each bounce keeps about the same fraction?
Provided example or reference data
Supplied example data: a tennis ball dropped from 100 cm onto a hard floor (average of 3 trials, rounded)
| Bounce | Height (cm) | Fraction of the height before |
|---|---|---|
| Drop | 100 | - |
| 1st bounce | 55 | about 0.55 |
| 2nd bounce | 30 | about 0.55 |
| 3rd bounce | 17 | about 0.55 |
| 4th bounce | 9 | about 0.5 |
Check the data source in the teacher lesson. Illustrative or fictional data are not measurements collected by your class.
Check understanding
What should pupils know? Name the energy forms of a bouncing ball, from being held up high to the top of its first bounce.
Explain with evidence: Use your data to predict the first bounce height if you dropped a tennis ball from 200 cm. Explain.
Apply the idea: Why do playgrounds use soft rubber matting under equipment? Use energy ideas.
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.