A delivery van travels along a straight road from a depot to a warehouse. For the first 20 seconds the van accelerates uniformly from rest. It then travels at a constant velocity of 18 m/s for 60 seconds. Finally, the van decelerates uniformly and comes to rest after a further 12 seconds. Describe what a velocity-time graph of the entire journey would look like, and state what feature of the graph could be used to find the total distance travelled.

Pearson Edexcel International GCSE Physics (4PH1) — 1.2 Movement and position · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

A straight‑line segment rising from 0 to 18 m s⁻¹ over 20 s (positive slope) – uniform acceleration.
A horizontal straight line at 18 m s⁻¹ for 60 s – constant velocity.
A straight‑line segment falling from 18 m s⁻¹ to 0 over 12 s (negative slope) – uniform deceleration.
The total distance travelled is the area under the whole curve.

Examiner tips

  • Show the three distinct straight‑line sections with correct slopes and time axes.
  • Label the axes and key points (0,18,0) clearly.
  • Explain that the area under the graph gives distance.
  • Use units (m) when stating the area result.

Common mistakes

  • Drawing a curved rather than straight line for uniform acceleration/deceleration.
  • Omitting the horizontal section or mis‑labeling the constant‑velocity part.
  • Failing to recognise that the area under the graph equals distance.

Mark scheme (4 marks)

  1. The first section of the graph is a straight line with a positive gradient (rising from zero to 18 m/s over 20 s), indicating uniform acceleration.
  2. The second section is a horizontal straight line at 18 m/s for 60 seconds, indicating constant velocity.
  3. The third section is a straight line with a negative gradient returning to zero (velocity decreasing uniformly from 18 m/s to 0 over 12 s), indicating uniform deceleration.
  4. The total distance travelled is found from the area under the velocity-time graph.

Key terms in this question

velocity-time graph · constant velocity · distance

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