# A sprinter runs 100 m along a straight track in 12.5 s, then immediately turns around and jogs back 40 m towards the start line before stopping. Describe the difference between the sprinter's total distance travelled and their displacement at the point they stop, and explain why their average speed and average velocity for the whole journey are different from each other.

> WJEC A-Level Physics (Wales) — 1.1 Basic physics quantities and motion · Describe and Explain · 5 marks

> A sprinter completes a 100 m race in 12.5 s, then turns and jogs back 40 m along the same straight track before stopping.

## Mark scheme (5 marks)

1. Total distance travelled is 140 m (100 m + 40 m)
2. Displacement is 60 m (in the original direction of travel / from start to final position)
3. Displacement is a vector quantity / has both magnitude and direction, whereas distance is a scalar (magnitude only)
4. Average speed uses total distance (140 m) in its calculation
5. Average velocity uses displacement (60 m) instead of total distance, so it gives a smaller / different value

## Key terms

- [distance](https://www.gradenine.co.uk/glossary/distance)
- [displacement](https://www.gradenine.co.uk/glossary/displacement)
- [average speed](https://www.gradenine.co.uk/glossary/average-speed)
- [average velocity](https://www.gradenine.co.uk/glossary/average-velocity)

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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-runs-100-m-along-cb410a3b) · Published by Druglandscape Ltd.