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

There are many kinds of work. There's electrical work, take the motor, you plug it into the wall, electricity makes the fan go around, that's electrical work. There's magnetic work.

我们复习一下大一,学过的功的概念：,物体在力的作用下，运动了一段距离。

麻省理工公开课 - 热力学与动力学课程节选