Well, we say at the top of the loop, when it goes up and comes down the velocity is 0.

在曲线顶端,当物体上升,然后速度为0时候

耶鲁公开课 - 基础物理课程节选

But it's not a big con, because you can set up experiments in free space far from everything, where objects will, in fact, maintain their velocity forever.

但这并不是个反例,因为你可以在一个远离一切的空间里做实验,在那里,物体可以永远保持现有速度

耶鲁公开课 - 基础物理课程节选

So, hopefully that kind of clears up that question. And, of course, when the velocity actually is zero, this equation that the de Broglie has put forth is valid for anything that has momentum, so if something does not have any velocity at all, it actually does not have momentum, so you can't apply that equation anyway.

能回答你的问题，当然，如果速度真的是零的话,德布罗意提出的这个方程,只对有动量的物体成立,所以如果一个东西没有速度，它没有动量，也就不能应用这个方程。

麻省理工公开课 - 化学原理课程节选

What it means is if you'd release a rock at that location one second before with a certain speed that we can calculate, it would've ended up here with precisely the position and velocity it had at the beginning of our experiment.

它的意义在于,若在该处以特定速度抛出一个物体,这个速度可通过计算得到,一秒之后,物体会运动至我们设定的起点,并且速度为我们设定的初速度

耶鲁公开课 - 基础物理课程节选