The piston has a cross-sectional area, a, and the force pressure is force per volume area.

我们以活塞系统为例，来说明膨胀功。

麻省理工公开课 - 热力学与动力学课程节选

So the force that you're pushing down on here is the external pressure times the area.

或者压缩功的概念,在活塞上施加压力。

麻省理工公开课 - 热力学与动力学课程节选

We know the pressure is equal to force per area.

我们知道压强等于力除以面积。

麻省理工公开课 - 热力学与动力学课程节选

Pressure is force per volume area.

气体就被压缩。

麻省理工公开课 - 热力学与动力学课程节选

So the real pressure is not quite the same because of this attractive force as it was, as it would be without the attractive forces.

气体压强,由于分子间的吸引作用,会比理想气体要小,这样，我们应该修正p的值。

麻省理工公开课 - 热力学与动力学课程节选