So if delta v is negative, in this case delta v is negative, OK, delta v is negative, pressure is a positive number, negative times negative is positive, work is greater than zero.

也就是当活塞,压缩气体的时候，做的功是正的，按照这一规定,我们需要在这里，加上一个负号，这是习惯规定。

麻省理工公开课 - 热力学与动力学课程节选

putting all those things together, if you looked at this question again we'd get 100% on it, 0 9 that our only option here is 0. 9, and that it's not the negative, it's the positive version, because we're talking about how much energy we have to put into the system in order to eject an electron.

把这些放在一起，你们再看一下题目,大家100%都能选对，我们唯一的选择就是这个，它不是负数，它是正的，因为我们说的，是要,把电子激发出来,需要提供的能量。

麻省理工公开课 - 化学原理课程节选