All lessons › Challenge: Think like a scientist › Lesson 2
Australian primary science · Years 5–6 (challenge) · Lesson 2 of 3
Galileo’s challenge
Inquiry question: Do heavier things fall faster, and why does a skydiver stop speeding up?
Marked no materials needed
Testing an idea
What students learn
Gravity pulls all objects towards Earth. When forces on an object are unbalanced, its motion changes (it speeds up, slows down or turns). When forces are balanced, its speed stays the same. Air resistance grows with speed until it balances gravity.
Success criteria
- I can describe balanced and unbalanced forces.
- I can explain why a flat sheet of paper falls slower than a scrunched one.
- I can use data to explain why a skydiver reaches a top speed.
Preparation and materials
Before this lesson: Students can describe gravity as a pull and air resistance as a force that slows falling things (Pushes, pulls and falls, Years 3–4), and can write a hypothesis (lesson 1).
- iPads with Bottlebrush Education open (nothing else needed) — 13 (one per pair)
- Projector or big screen — 1
Teacher setup
- Open Forces & energy › Lab › Drop test on your screen to demonstrate.
- Check the iPads are charged and set to Your year › Years 5–6.
Safety and adaptations
Follow school science and equipment risk assessment procedures for the materials used.
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.
- Pairs test all four pairs in Drop test, predicting first.
- For each pair, draw a force diagram for each object while it is falling, with arrow lengths showing the size of each force.
- Read the skydiver data table and describe how the speed changes.
- Draw force diagrams for the skydiver at 0 s, 4 s and 12 s.
- Write a claim, evidence and reasoning answer to the puzzle.
Teacher modelling prompt
Open Drop test on the big screen and choose the flat sheet and scrunched sheet of paper. Think aloud: “They weigh the same, so gravity pulls equally on both. But the flat sheet has a much bigger area pushing against the air. I predict the scrunched one lands first.” Run it. Then drop two real sheets of scrap paper in front of the class, one flat and one scrunched, and draw force arrows for each.
Record and explain evidence
Recording question: Do heavier things fall faster, and why does a skydiver stop speeding up?
| Falling object or time | Gravity arrow (size) | Air resistance arrow (size) | Balanced or unbalanced? | What happens to the speed? |
|---|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
Use the force diagrams to decide who is right.
Provided example or reference data
Model data: a skydiver’s speed after jumping (belly-down, rounded)
| Time after jumping (s) | Speed (km/h) |
|---|---|
| 0 | 0 |
| 2 | about 68 |
| 4 | about 125 |
| 6 | about 160 |
| 8 | about 180 |
| 10 | about 190 |
| 12 | about 195 |
| 14 | about 195 |
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? What is the difference between balanced and unbalanced forces?
Explain with evidence: Use the skydiver data to explain why her speed stops increasing after about 12 seconds.
Apply the idea: When the skydiver opens her parachute, she slows down. Draw or describe the forces and explain.
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.