A car travels along a straight road. For the first part of the journey, the car accelerates uniformly from rest. It then travels at a constant speed before the driver applies the brakes and the car decelerates uniformly to a stop. Describe the motion of the car during each of the three stages of the journey, referring to how the speed changes in each stage.

Edexcel GCSE Physics (1PH0) — 2.1 Motion · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

During the first stage the car starts from rest and its speed increases steadily as it accelerates uniformly.
During the second stage the car travels at a constant, steady speed – its speed does not change.
During the third stage the driver brakes and the car decelerates uniformly, so its speed decreases until it comes to a stop.
At the end of the third stage the car’s final speed is zero.

Examiner tips

  • Use the word ‘accelerates’ for the first stage, ‘constant speed’ for the second, and ‘decelerates’ for the third.
  • Show the change in speed (increase, none, decrease) to match the mark scheme.
  • Mention that the final speed is zero to secure the last point.

Common mistakes

  • Confusing ‘accelerates’ with ‘decelerates’ in the first stage.
  • Failing to state that the speed is zero at the end of the journey.
  • Using vague terms like ‘goes faster’ instead of ‘increases’.

Mark scheme (4 marks)

  1. During the first stage, the car's speed increases (from zero / from rest)
  2. During the second stage, the car travels at a constant / steady speed (no change in speed)
  3. During the third stage, the car decelerates / its speed decreases
  4. The car's final speed is zero / the car comes to a stop (at the end of the third stage)

Key terms in this question

constant speed

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