# A cyclist travels along a straight road. For the first part of the journey the cyclist moves with a constant positive velocity, then decelerates uniformly to rest. Explain how the instantaneous acceleration of the cyclist differs from the average acceleration over the entire journey, and state the sign of each.

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

## Mark scheme (4 marks)

1. Instantaneous acceleration is zero during the constant-velocity phase
2. Instantaneous acceleration is negative (and constant) during the deceleration phase
3. Average acceleration is defined as total change in velocity divided by total time taken
4. Average acceleration is negative but has a smaller magnitude than the instantaneous acceleration during deceleration, because the total time includes the constant-velocity phase where no acceleration occurs

## Key terms

- [instantaneous acceleration](https://www.gradenine.co.uk/glossary/instantaneous-acceleration)
- [average acceleration](https://www.gradenine.co.uk/glossary/average-acceleration)

## 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-cyclist-travels-along-a-straight-95694dbc) · Published by Druglandscape Ltd.