"Want me to go back along with you in the cart and wind it for you,Ranse?"

VOA: special.2009.11.14

if you've got a hill or valley and there's a cart on wheels it's going to go down to the bottom.

如果我们有一座山或者山谷，并且,有一个有轮子的车，这辆车会自动滑到底部。

麻省理工公开课 - 热力学与动力学课程节选