# A sprinter accelerates uniformly from rest and reaches a maximum velocity of 11 m s⁻¹ at the end of the first 4.0 s of a race. The sprinter then maintains this maximum velocity for the remainder of the race. Explain how the gradient of a displacement–time graph for this sprinter would differ between the first 4.0 s and the period after 4.0 s, and describe the shape of the displacement–time graph during each phase.

> IB DP Physics Higher Level (2023 syllabus) — A.1 Kinematics · Explain · 4 marks

## Mark scheme (4 marks)

1. During the first 4.0 s the gradient of the displacement–time graph increases (from zero) / the gradient is not constant.
2. The gradient equals the instantaneous velocity, so an increasing gradient reflects the increasing velocity / acceleration of the sprinter during this phase.
3. After 4.0 s the gradient is constant / the gradient does not change.
4. The shape of the graph is a curve (concave upward / increasing slope) during the first 4.0 s and a straight line with a steeper/positive gradient after 4.0 s.

## Key terms

- [displacement–time graph](https://www.gradenine.co.uk/glossary/displacement-time-graph)
- [gradient](https://www.gradenine.co.uk/glossary/gradient)

## Related

- [Revision notes for IB DP Physics Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-sprinter-accelerates-uniformly-from-rest-e586818b) · Published by Druglandscape Ltd.