Year 7 Science · Unit 3 · Lesson 3

Friction — Types and Effects

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Learning Goals

Sequence the process of aquaplaning using correct scientific reasoning.
Apply knowledge of friction types to explain a real-world engineering problem.
Distinguish between different types of friction in a racing context.

Warm Up

Order the steps

Number the events from 1 to 7 to show the correct order of what happens when a car aquaplanes on a wet Australian highway. Event 1 = what happens first.

Order (1–7)	Event
	The car's stopping distance increases dramatically — the driver cannot brake effectively.
	The driver loses steering control because the tyres are no longer gripping the road surface.
	Rain falls on the road and forms a thin film of water on the bitumen surface.
	Without tyre–road contact, rolling friction between the tyre and road drops to near zero.
	The car travels over the wet road at speed; its tyres cannot displace the water fast enough.
	A wedge of water builds up under the tyre, causing the tyre to lift off the road surface.
	The tyre is now riding on water — fluid friction (drag) replaces rolling friction as the dominant resistive force.

Your Turn

Real-world context

In Formula 1 motor racing, tyre choice is one of the most critical engineering decisions. In dry conditions, teams use "slick" tyres — completely smooth, with no tread pattern at all. But in wet conditions, teams must switch to grooved wet-weather tyres, which have deep channels cut into the rubber. At the 2023 Australian Grand Prix at Melbourne's Albert Park circuit, a safety car was deployed when rain fell during the race, triggering a flurry of tyre changes in the pit lane.

(a) Use your knowledge of friction types to explain why smooth slick tyres provide better grip than grooved tyres in dry conditions. Refer to the type(s) of friction involved and what factors affect friction magnitude.

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(b) Explain why slick tyres become dangerous in wet conditions, and how grooved wet-weather tyres solve this problem. Use the term "aquaplaning" in your answer.

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Show What You Know

1. Australian road safety guidelines recommend replacing car tyres when tread depth falls below 1.5 mm. Explain why worn, shallow tread is particularly dangerous in wet weather, using friction types in your answer.

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2. A cyclist on a mountain bike trail increases their braking force significantly when approaching a mud section. Predict what will happen to (a) the friction between tyre and ground, and (b) the risk of skidding. Explain your reasoning.

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Wrap Up

In one sentence, what was the main idea of this lesson?