A diver descends from the surface of the sea to a depth of 30 m. Explain why the pressure acting on the diver increases as the diver descends.

Cambridge International IGCSE Physics (0625) — 1.8 Pressure · 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 in a liquid increases with depth.
The diver is surrounded by a column of water whose height is greater the deeper he goes.
The weight of this column of water therefore increases as the depth increases.
This greater weight (force) acts over the same area of the diver’s body, so the pressure increases.

Examiner tips

Use the term ‘column of water’ and ‘weight of the column’ to show understanding of the cause.
Show that the same area is involved – pressure = force/area – to link force and pressure.
Mention that the increase is linear with depth – a key point examiners look for.

Common mistakes

Confusing pressure with force – forgetting to divide by area.
Saying only that the water is ‘hotter’ or ‘denser’ – irrelevant to pressure increase.
Using vague phrases like ‘more water’ without explaining the column concept.

Mark scheme (4 marks)

Pressure in a liquid increases with depth
There is a greater column (height) of water above the diver at greater depth
The weight of the water above the diver increases (as depth increases)
This greater weight (force) acts over the same area, so pressure increases

Key terms in this question

pressure · depth