Whether you take the elevator to the top of the Hancock Tower or whether you walk up the stairs, the change in gravitational potential is identical.

不管你是乘电梯,去大厦的顶层,或者是步行，重力势能的变化是相同的。

麻省理工公开课 - 固态化学导论课程节选

You need to walk down the stairs and then up the stairs.

要被迫上下楼。

哈佛公开课 - 幸福课课程节选