Physics (AS & A Level) · Oct / Nov 2018 · Paper 11 · Question 15

A mass $m$ is on top of a platform that is supported by gas in a cylinder of cross-sectional area $A$, as shown. The platform has negligible mass and can move freely up and down. The gas is heated and expands so that the mass is raised through a height $h$. Atmospheric pressure is $p$. What is the ratio $\dfrac{\text{gain in gravitational potential energy of the mass}}{\text{work done by the gas}}$?

1. A$\dfrac{mg}{pA}$
2. B$\dfrac{mg}{mg + pA}$
3. C$\dfrac{pA}{mg}$
4. D$\dfrac{mg - pA}{mg}$

As printed in the paper