First, take the case in the elevator is on the ground floor of some building and completely addressed.

首先我们来看看电梯,在一楼时候的情况

耶鲁公开课 - 基础物理课程节选

As you come to the top of the building, the elevator has to decelerate, so that it loses its positive velocity and comes to rest.

当你要到顶时,电梯需要减速,此时电梯速度减小最后静止

耶鲁公开课 - 基础物理课程节选