The advantage of introducing that guy is that if you like, I can now write an equation for the acceleration as a vector.

引入它的好处是,如果你愿意的话,我可以把加速度写成矢量形式

耶鲁公开课 - 基础物理课程节选

I want to consider a particle which has definite acceleration a, a constant one, but a is now a vector.

我想考虑一个加速度为 a 的质点,加速度恒定,但 a 是一个矢量

耶鲁公开课 - 基础物理课程节选

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