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Australian primary science · Year 4 · Lesson 3 of 4
Rough or smooth?
Inquiry question: Which surface makes a car stop in the shortest distance?
Check practical materials
Fair testing
What students learn
Friction is a force that slows moving things. Rough surfaces make more friction than smooth ones.
Success criteria
- I can change only the surface.
- I can measure and repeat.
- I can explain my results using the word friction.
Preparation and materials
Before this lesson: Students can run a ramp fair test (lesson 2).
- Ramps and books from lesson 2 — 13 sets
- Surfaces: carpet square, towel, smooth board, sandpaper, bubble wrap — 13 sets
- Toy cars and tape measures — 13
Teacher setup
- Cut surface strips at least 1.5 m long, or use a 1-book ramp so the car stops on the surface.
Safety and adaptations
- Hold sandpaper by the edges.
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.
- Predict which surface stops the car soonest.
- Lay a surface at the bottom of the ramp.
- Release the car from the same height; measure the distance.
- Repeat 3 times per surface.
- Order surfaces from most to least friction.
Teacher modelling prompt
Rub hands together slowly, then quickly: “I can feel them resist and get warm. That is friction.” Then model the plan: change the surface only; same ramp height and car.
Record and explain evidence
Recording question: Which surface makes a car stop in the shortest distance?
| Surface | Trial 1 (cm) | Trial 2 (cm) | Trial 3 (cm) |
|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
Which explanation uses a science idea?
Check understanding
What should pupils know? What is friction?
Explain with evidence: Use your results to say which surface had the most friction.
Apply the idea: Why do we put sand on icy paths?
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.