A car is travelling along a road when the driver notices ice on the road surface ahead. Describe the effect of icy road conditions on the thinking distance and braking distance of the car, and explain why the total stopping distance is increased.

OCR GCSE Physics A: Gateway Science (J249) — P8 Global challenges · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Road safety experts warn that stopping distances can increase significantly in winter conditions, particularly when ice is present on the road surface.

Model answer (4 marks)

Thinking distance is not affected by icy road conditions.
Braking distance is increased by icy road conditions.
Ice reduces the friction between the tyres and the road.
Because stopping distance is the sum of thinking distance and braking distance, and braking distance has increased, the total stopping distance is greater.

Examiner tips

  • Use the exact terms: thinking distance, braking distance, stopping distance. Show the relationship: stopping distance = thinking distance + braking distance. Explain that friction loss increases braking distance. Keep answer to four short points to match marks.

Common mistakes

  • Confusing thinking distance with braking distance. Claiming thinking distance increases on ice. Forgetting to mention friction as the cause of increased braking distance.

Mark scheme (4 marks)

  1. Thinking distance is not affected by icy road conditions / thinking distance remains the same
  2. Braking distance is increased by icy road conditions
  3. Ice reduces the friction between the tyres and the road
  4. Because stopping distance is the sum of thinking distance and braking distance, and braking distance has increased, the total stopping distance is greater

Key terms in this question

thinking distance · braking distance · stopping distance

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