We start at p1, V1. and p external is equal to zero.

从状态开始，外部压强为零。

麻省理工公开课 - 热力学与动力学课程节选

to take my cylinder now, and the external pressure and the internal pressure are not going to be I'm going to start with my cylinder here, I'm going to put little pegs here so it doesn't fly up.

活塞内外的，压强不相等,我们在,放上插销，以防止活塞。

麻省理工公开课 - 热力学与动力学课程节选