And at a distance of 2 r naught, I have a positive repulsive term.

在这2r圈的距离上，这里有一个不可忽略的排斥场。

麻省理工公开课 - 固态化学导论课程节选

So I have a distance here of 2 r naught.

因为有一个2r圈的距离。

麻省理工公开课 - 固态化学导论课程节选

You can take a derivative of the derivative and you can get the acceleration vector, will be d^2r over dt^2, and you can also write it as dv over dt.

你可以对导数再求一次导,你就可以得到加速度矢量,也就是 d^2 r / dt^2,你也可以写成 dv / dt

耶鲁公开课 - 基础物理课程节选

You don't need Born repulsion at 2 r naught.

我们不需要在r等于2r圈处的Born力。

麻省理工公开课 - 固态化学导论课程节选