The gas in an engine does work on a piston of cross-sectional area 80 cm2. The pressure on the piston has a constant value of 4.6 × 105 Pa.

Question 17

The gas in an engine does work on a piston of cross-sectional area 80 cm². The pressure on the piston has a constant value of 4.6 × 10⁵ Pa.

How much work is done by the gas on the piston when it moves through a distance of 25 cm?

A 9.2 × 10² J                        B 9.2 × 10⁴ J                        C 9.2 × 10⁶ J            D 9.2 × 10⁸ J

Reference: Past Exam Paper – June 2015 Paper 13 Q17

Solution:

Answer: A.

For a constant pressure,

Work done = pressure × change in volume

Work done = p × ΔV

As the gas in the engine does work on the piston, there is a change in volume.

ΔV = cross-sectional area × distance moved

ΔV = 80×10^-4 × 0.25 = 0.002 m³

Work done = p × ΔV

Work done = 4.6×10⁵ × 0.002

Work done = 920 J = 9.2×10² J