How is pressure different from force?

Force is in newtons; pressure is force divided by area in pascals, so it measures how concentrated the force is.

Which formulas must be known?

P = F / A, P = rho g h and upthrust = rho x g x displaced volume, each with units.

S4 Physics pressure and fluids paper 1: ten formula items

2026-11-10

Tutor Prep Guide · S4 Physics Pressure and Fluids

Ten items start from P = F / A and P = rho g h, all in DSE units, with area converted first.

Direct answers　Items 01 to 03 cover basic and liquid pressure, 04 to 06 reverse for force and pressure difference, 07 to 09 test unit conversion and deep water. Allow 25 minutes.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	25
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: S4 Physics Pressure and Fluids
Level	S4

02　Questions (10 items)

FoundationA force of 200 N acts at right angles on an area of 0.5 m squared. Find the pressure.
FoundationA student of weight 600 N stands with both feet covering 0.04 m squared. Find the pressure on the floor.
FoundationFind the water pressure at a depth of 2 m (density 1000 kg per cubic metre, g = 10 N/kg).
IntermediateA pressure of 500 Pa acts on an area of 0.2 m squared. Find the total force.
IntermediateAtmospheric pressure is 100000 Pa. Find the force it exerts on a window of area 0.02 m squared.
IntermediateFind the difference in water pressure between depths of 1 m and 3 m (density 1000, g = 10).
ChallengeA force of 2000 N acts on an area of 50 cm squared. Find the pressure in Pa.
ChallengeA diver is at 15 m depth. Find the water pressure and the total pressure (atmosphere 100000 Pa).
ChallengeA skater of weight 600 N stands on one blade of area 0.001 m squared. Find the pressure on the ice.
Error redoA pupil says liquid pressure depends only on the total weight of liquid. What is wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	400 Pa	P = F / A = 200 / 0.5 = 400 Pa; the unit is newtons per square metre.
2	15000 Pa	P = 600 / 0.04 = 15000 Pa; the area is the total for both feet.
3	20000 Pa	P = rho x g x h = 1000 x 10 x 2 = 20000 Pa; only density and depth matter.
4	100 N	F = P x A = 500 x 0.2 = 100 N; multiply pressure by area to get force.
5	2000 N	F = P x A = 100000 x 0.02 = 2000 N; the air pushes on both sides, so the glass does not break.
6	20000 Pa	Only the 2 m difference counts: 1000 x 10 x 2 = 20000 Pa.
7	400000 Pa	50 cm squared is 0.005 m squared, so P = 2000 / 0.005 = 400000 Pa; convert units first.
8	Water pressure 150000 Pa; total 250000 Pa	Water pressure = 1000 x 10 x 15 = 150000 Pa, and adding the atmosphere gives the total.
9	600000 Pa	P = 600 / 0.001 = 600000 Pa; a smaller area gives a larger pressure, which is why blades bite the ice.
10	Liquid pressure depends only on density and depth (P = rho g h), not on the shape of the vessel or the total amount.	At the same depth in the same liquid the pressure is the same, however wide or narrow the vessel.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

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