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

Remember back to Alexander H. Steven's cornerstone quote he uses the word "Natural" Twice in that passage.

还记得亚历山大·斯蒂文的柱石上的引文,这段引文中他用了"自然"这个概念两次

耶鲁公开课 - 美国内战与重建课程节选