A diver descends from the surface of the sea to a depth of 30 m. Explain how the pressure acting on the diver changes as they descend, and state TWO effects this increased pressure could have on the diver's body.

Eduqas GCSE Physics — 3.2 Pressure and pressure differences in fluids · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Pressure increases as the diver descends deeper because the weight of the water column above the diver increases with depth.

The increased pressure can:
1. Cause pain or damage to the ears and eardrums as the pressure inside the middle ear is not equalised.
2. Compress the lungs and chest, making breathing harder and increasing the risk of gas dissolution in the blood (decompression sickness) on ascent.

Examiner tips

  • Use the phrase ‘pressure increases as the diver descends deeper’ to show understanding of hydrostatic pressure. Include the reason ‘weight of the water column above the diver increases’. Give two distinct, valid physiological effects (e.g. ear pain, lung compression, decompression sickness).

Common mistakes

  • Writing that pressure decreases with depth. Giving effects that are not related to pressure, such as temperature changes. Using vague terms like ‘more pressure’ without explaining why it increases.

Mark scheme (4 marks)

  1. Pressure increases as the diver descends deeper
  2. Because the weight / column of fluid above the diver increases (as depth increases)
  3. One valid effect on the diver's body — e.g. ears / eardrums experience pain or can be damaged / compressed
  4. A second valid effect on the diver's body — e.g. lungs / chest compressed / breathing becomes harder / gases dissolve into blood causing decompression sickness on ascent

Key terms in this question

pressure · depth

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