好，让我们看看重物的质量,以及它下落的距离，就知道桨轮做了多少功。

So, it's a trivial matter, by looking at what is the weight and how far does it drop, to say OK, how much work is done by the paddle wheel.

youdao

如果用频闪相机拍摄，苹果下落的过程，可以看到频闪的间隔，苹果的距离，随着时间不断变大，因为速度随着时间而变大。

So if I strobe this apple while it was falling I would see the separation, when it strobes to increase with time, because the velocity goes up with time.

youdao

需要声明的是，在上述表达式中，我用a表示跳楼者的最大加速度。 此外，我还假设跳楼者完全停下所经过的距离与整个下落距离相比可以忽略不计。

Just to be clear, I am putting the maximum acceleration in for a. Also, I have made the assumption that the stopping distance (s) is small compared to the jumping height.

youdao

So, it's a trivial matter, by looking at what is the weight and how far does it drop, to say OK, how much work is done by the paddle wheel.

好，让我们看看重物的质量,以及它下落的距离，就知道桨轮做了多少功。

麻省理工公开课 - 热力学与动力学课程节选