We divide that by the mass, so 0.12 kilograms, that's the mass of a regulation baseball for the major leagues, and the velocity of the baseball is 42 meters per second. So, we can cross out our units doing our unit analysis.

我们用质量来除它，质量为0，12千克，这是大多数联赛规定的棒球质量,棒球的速度为42米每秒,所以，我们可以消去单位,来做单位分析。

麻省理工公开课 - 化学原理课程节选

It's always good when we're looking for a wavelength that our answer is in a unit of length, that's a good sign already.

当我们计算波长时,如果答案是一个长度单位，那就是一个好的迹象。

麻省理工公开课 - 化学原理课程节选