Physics (AS & A Level) · Feb / March 2017 · Paper 12 · Question 17

A gas is enclosed inside a cylinder which is fitted with a frictionless piston. Initially, the gas has a volume V_1 and is in equilibrium with the external pressure p. The gas is then heated slowly so that it expands at constant pressure, pushing the piston back until the volume of the gas has increased to V_2. How much work is done by the gas during this expansion?

1. Ap(V_2 - V_1)
2. B\frac{1}{2}p(V_2 - V_1)
3. Cp(V_2 + V_1)
4. D\frac{1}{2}p(V_2 + V_1)

As printed in the paper