Our piston on the right side here fully out, and the piston on my right side, your left side, fully inside. There's no gas p1 on that side here. So there's p2 sitting here.

左边的这个活塞完全在外面，而右边的左边的这个活塞完全在里面，这边没有一点空气,这边是P2，这边是。

麻省理工公开课 - 热力学与动力学课程节选