# A ball is thrown vertically upwards and returns to its starting position. Explain why the average speed of the ball over the entire journey is greater than zero whilst its average velocity is zero.

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

## Mark scheme (4 marks)

1. Average velocity is zero because displacement is zero — the ball returns to its starting position, so net change in position is zero.
2. Average velocity is defined as displacement divided by time, so zero displacement gives zero average velocity regardless of the time taken.
3. Average speed is greater than zero because the ball has travelled a non-zero total distance (up and then back down).
4. Average speed is defined as total distance divided by time, which is a scalar quantity, so the distances on the way up and the way down add together rather than cancelling.

## Key terms

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

## 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-ball-is-thrown-vertically-upwards-4a0056fe) · Published by Druglandscape Ltd.