Units (Solids, Liquids and Gases)
4 marks · EasyA diver descends in the sea to a depth of 15 m. The density of seawater is 1025 kg/m³. Take gravitational field strength g = 10 N/kg.
Calculate the increase in pressure on the diver at this depth, relative to the surface.
Describe how pressure in a liquid acts on the diver at this depth.
Explain how the force on a part of the diver’s body can be calculated using pressure and area.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) 153,750 Pa
(b) Pressure in a liquid acts equally in all directions.
(c) Force can be calculated using F = p × A, where A is the area of the body part.
Common mistakes: using wrong values in formula; incorrect units
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Writes correct formula and substitutes: p = h x ρ x g = 15 x 1025 x 10.
A1 (a) · 1 mark · Correct final answer: 153,750 Pa with correct unit. (follow-through)
B1 (b) · 1 mark · States that pressure acts equally in all directions in a non-moving fluid.
B2 (c) · 1 mark · Correct statement that force equals pressure multiplied by area, with formula F = p × A or equivalent.
Worked solution
a) Pressure difference:
b) In liquids, pressure acts equally in all directions at a given depth when stationary.
c) The force on a surface is calculated using F = p × A, where A is the area of the surface.