10 liters of air are compressed at a constant pressure of 100 kPa to a volume of 7 liters. What work have external forces done?

Given:

p = 100 kPa = 10⁵ Pa;

V1 = 10 l = 0.01 m³;

V2 = 7 l = 0.007 m³;

Let’s find a gas job.

A = p * (V2 – V1) = 10⁵ * (0.007 – 0.01) = 10⁵ * (-0.003) = -3 * 10² J – work of gas.

The work of external forces is opposite to the work of gas, that is:

A ext = – A gas.

A ext = – (-3 * 10² J) = 3 * 10² J = 300 J.

Answer 300 J.