O-LevelPhysicsThermal Physics5054/12 · Oct/Nov 2025 · Q221 Mark

Air is trapped in a glass tube by a liquid. When the tube is horizontal, the length of the trapped air is 50 mm and its pressure is 1.0 × 10⁵ Pa. [Figure 22.1] When the tube is vertical, with the closed end downwards, the length of the trapped air is 45 mm. The temperature of the air remains constant. What is the pressure of the trapped air when the tube is vertical?

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A0.50 × 10⁵ Pa

B0.90 × 10⁵ Pa

C1.1 × 10⁵ Pa

D1.9 × 10⁵ Pa

✓ Correct answer

C: 1.1 × 10⁵ Pa

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Topic: Thermal Physics, O-Level Physics (syllabus 5054). Multiple choice, 1 mark.
Source: O-Level Physics, Oct/Nov 2025 Paper 1 Variant 2, question 22.

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