Occasionally, you'll find you need to cancel out units, because, of course, you're always doing unit analysis as you solve your problems, and sometimes you'll need to convert joules to kilogram meters square per second squared.

偶然地，你会发现需要消除单位，因为在解题时,经常要做单位分析，所以有时候需要把,焦耳换做,一千克乘以米的平方除以秒的平方。

化学原理课程节选 : 麻省理工公开课