# A scientist is studying pressure differences in the ocean. Explain why a sealed plastic bottle, which is partially filled with air, becomes crushed as it is pushed deeper below the water surface.

> Eduqas GCSE Physics — 3.2 Pressure and pressure differences in fluids · Explain · 4 marks

> A sealed plastic bottle containing some air is pushed downwards from the ocean surface to a depth of several hundred metres.

## Mark scheme (4 marks)

1. Pressure in a fluid increases with depth
2. This is because the weight / column of water above the bottle increases as depth increases
3. The water exerts pressure on all surfaces of the bottle / the pressure acts inwards on the bottle
4. The increased pressure force from the water is greater than the pressure of the trapped air inside, so the bottle is crushed / compressed

## Key terms

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

## Related

- [Revision notes for Eduqas GCSE Physics](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-scientist-is-studying-pressure-differences-00342f21) · Published by Druglandscape Ltd.