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S4 Physics: Pressure and Upthrust Paper 4 (Error Redo)
S4 Physics: Pressure and Upthrust Paper 4 (Error Redo)
This paper reworks five recurring slips: unconverted units, weight over depth as pressure, full volume for a floating body, wrong depth reference, and volume-dependent pressure.
Quick answer 1. 10,000 Pa | 2. 40,000 Pa | 3. 30 N | 4. 10 N and 1,000 cm3 | 5. 200 N, 0.02 m3 immersed | 6. 50,000 Pa and 10,000 N | 7. 12.6 percent | 8. 120 kPa | 9. 27 N in air, 17 N in water | 10. depth, density and g only
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 | Error redo |
02 Questions (10 items)
- FoundationA 300 N force acts on 0.03 m2. What is the pressure and its unit?
- FoundationWhat is the water pressure at 4 m depth?
- FoundationAn object of volume 0.003 m3 is fully immersed in water. What is the upthrust?
- FoundationA stone weighs 25 N in air and 15 N in water. Find the upthrust and the volume.
- IntermediateA 0.05 m3 block of density 400 kg/m3 floats. Find the upthrust and the immersed volume.
- IntermediateA 0.001 m2 piston is pushed with 50 N and drives a 0.2 m2 piston. Find the transmitted pressure and the force.
- IntermediateAn iceberg of density 900 kg/m3 floats in water of density 1,030 kg/m3. What percentage shows above the surface?
- ChallengeA tank surface is 15 m above ground; a third-floor tap is 3 m above ground. What is the pressure at the tap in kPa?
- ChallengeA 0.001 m3 aluminium block (2,700 kg/m3) hangs from a spring balance, first in air then in water. Find both readings.
- Error redoA student claims a wider container holding more water always gives higher base pressure. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | P = 300 / 0.03 = 10000 Pa, that is N/m2. | The pascal is one newton per square metre. |
| 2 | P = 1,000 x 10 x 4 = 40000 Pa. | This one is just the three numbers in pgh multiplied. |
| 3 | U = 1,000 x 0.003 x 10 = 30 N. | Full immersion uses the object volume, not its mass. |
| 4 | Upthrust = 25 – 15 = 10 N; V = 10 / 10,000 = 0.001 m3 = 1000 cm3. | The drop in apparent weight is the upthrust; divide by pg for the volume. |
| 5 | Weight = 400 x 0.05 x 10 = 200 N, so upthrust = 200 N; immersed = 200 / 10,000 = 0.02 m3. | For a floating body go from density to weight, then back to displaced volume. |
| 6 | P = 50 / 0.001 = 50000 Pa; F = 50000 x 0.2 = 10000 N. | The pressure passes through unchanged; force scales with area. |
| 7 | Immersed = 900 / 1,030 = 0.8738, so 12.6 percent is exposed. | The density ratio fixes the immersed part, usually about nine tenths. |
| 8 | Depth = 15 – 3 = 12 m; P = 1,000 x 10 x 12 = 120000 Pa = 120 kPa. | Depth is measured to the outlet, not to the floor level. |
| 9 | In air = 27 N; upthrust = 10 N; reading in water = 17 N. | Apparent weight is weight minus upthrust, and upthrust depends on displaced volume only. |
| 10 | Wrong: liquid pressure depends only on depth, density and g, not on shape or volume. | Same depth and liquid mean the same pressure, which underlies connected vessels. |
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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