What is the water pressure at 5 m depth?

P = pgh = 1,000 x 10 x 5 = 50000 Pa = 50 kPa.

What force acts on a 2 m2 gate 20 m deep?

P = 1,000 x 10 x 1.5 = 15000 Pa.

What can a hydraulic jack with a 250 times area ratio lift?

P = 1,000 x 10 x 20 = 200000 Pa; F = P x A = 200000 x 2 = 400000 N.

S4 Physics: Pressure and Upthrust Paper 2 (Liquid Pressure and Connected Vessels)

2026-11-03

S · 4

This paper drills liquid pressure against depth, equal levels in connected vessels, the area ratio in a hydraulic press, and tank and hull applications.

Quick answer　1. 50,000 Pa (50 kPa) | 2. 15,000 Pa | 3. 400,000 N | 4. equal levels | 5. 25,000 N | 6. about 10.3 m of water | 7. all the same, 10,000 Pa | 8. 110 kPa | 9. 60 N | 10. 20,000 Pa

01　Paper details (check answers afterwards)

Item	Detail
Questions	10 questions
Suggested time	25 minutes
Difficulty mix	Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1
Chapter	Chapter: S4 Physics – Pressure and Upthrust
Level	Application

02　Questions (10 items)

FoundationAt a depth of 5 m, what is the water pressure in Pa, and in kPa? (density 1,000 kg/m3, g = 10 N/kg)
FoundationWhat is the pressure at 1.5 m depth in the same pool?
FoundationA gate of area 2 m2 sits 20 m deep on a dam. What total force does the water exert on it?
FoundationTwo connected tubes of different widths hold the same liquid at rest. How do the levels compare?
IntermediateA hydraulic jack has a 0.002 m2 small piston pushed with 100 N and a 0.5 m2 large piston. What force can the large piston lift?
IntermediateMercury has density 13,600 kg/m3. A 76 cm mercury column equals what height of water column?
IntermediateThree differently shaped containers all hold water 1 m deep. How do the base pressures compare?
ChallengeA water tank surface is 12 m above ground and a tap is 1 m above ground. What is the pressure at the tap in kPa?
ChallengeA 20 cm2 hole in a hull is 3 m below the surface. What force is needed to hold it shut?
Error redoA student divides the water weight 10,000 N by the 2 m depth and gets 5,000 Pa for a pool 2 m deep. What is correct?

03　Answers and one-line notes

#	Answer	One-line note
1	P = pgh = 1,000 x 10 x 5 = 50000 Pa = 50 kPa.	Liquid pressure uses only depth, density and g.
2	P = 1,000 x 10 x 1.5 = 15000 Pa.	A third of the depth gives a third of the pressure.
3	P = 1,000 x 10 x 20 = 200000 Pa; F = P x A = 200000 x 2 = 400000 N.	Find the pressure at that depth, then multiply by the area.
4	The two levels lie on the same horizontal line, whatever the tube widths.	For one liquid at rest, levels in connected vessels are equal.
5	P = 100 / 0.002 = 50000 Pa; F = 50000 x 0.5 = 25000 N.	A hydraulic press passes pressure on, so force scales with the area ratio.
6	Height is inversely proportional to density: 0.76 x 13.6 = 10.336 m, about 10.3 m of water.	A 13.6 times denser liquid needs a 13.6 times shorter column.
7	All three are the same, P = 1,000 x 10 x 1 = 10000 Pa.	Liquid pressure ignores volume and shape, only depth matters.
8	Depth = 12 – 1 = 11 m; P = 1,000 x 10 x 11 = 110000 Pa = 110 kPa.	Depth runs from the free surface to the outlet, not to the ground.
9	P = 1,000 x 10 x 3 = 30000 Pa; 20 cm2 = 0.002 m2; F = 30000 x 0.002 = 60 N.	Force is pressure times area, with the area converted to square metres.
10	P = pgh = 1,000 x 10 x 2 = 20000 Pa, independent of volume and base area.	Pressure is not weight over depth; use P = pgh directly.

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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