Physics · Oct / Nov 2025 · Paper 12 · Question 22

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. [diagram: horizontal tube with air and thread of liquid, 50 mm; vertical tube with thread of liquid and air, 45 mm] 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?

1. A0.50 × 10⁵ Pa
2. B0.90 × 10⁵ Pa
3. C1.1 × 10⁵ Pa
4. D1.9 × 10⁵ Pa

As printed in the paper