# A cargo ship is travelling across the ocean at a constant velocity. The ship's engines produce a driving force. Explain why the ship travels at a constant velocity rather than accelerating.

> OCR GCSE Physics A: Gateway Science (J249) — P2.3 Forces in action · Explain · 4 marks

> A large cargo ship cruises at a steady speed across the ocean. Its engines are running and producing a continuous driving force forwards. Despite this, the ship does not speed up.

## Mark scheme (4 marks)

1. The ship experiences a resistive force (friction / drag / water resistance) acting in the opposite direction to motion
2. The driving force and the resistive force are equal in magnitude / balanced
3. The resultant force on the ship is zero
4. According to Newton's First Law, an object with a resultant force of zero continues at a constant velocity

## Key terms

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

## Related

- [Revision notes for OCR GCSE Physics A: Gateway Science (J249)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-cargo-ship-is-travelling-across-747cb248) · Published by Druglandscape Ltd.