Q6 — Stopping distance (4 marks)

Explain why a car's stopping distance increases on a wet road. Refer to the two components of stopping distance in your answer. (4 marks)

Mark scheme (4 marks):

• Stopping distance = thinking distance + braking distance (1)
• Thinking distance is unchanged by wet road (depends on driver reaction time) — accept if stated (1)
• Braking distance increases on wet roads because friction between tyres and road is reduced (1)
• Reduced friction means less deceleration / less work done against friction per metre, so the car travels further before stopping (1)