Physics (AS & A Level) · Oct / Nov 2017 · Paper 12 · Question 15

Air is trapped inside a glass bulb which is immersed in water and attached to a U-tube containing mercury. The densities of water and mercury are ρw and ρm respectively. The surface of the water is open to the atmosphere where atmospheric pressure is P. The acceleration of free fall is g. What is the pressure of the air in the glass bulb?

1. AP + gρwhw + gρmhm
2. BP + gρwhw – gρmhm
3. Cgρwhw + gρmhm
4. Dgρwhw – gρmhm

As printed in the paper