You can actually take derivatives of a vector with time.

你可以直接求位矢对时间的导数

耶鲁公开课 - 基础物理课程节选

Just take the derivatives and that's the velocity vector.

直接计算对时间的导数就是速度矢量

耶鲁公开课 - 基础物理课程节选

And the mathematics of that equation involved a double derivative in time of x 0 plus some constant times x equals zero with some constraints on it.

那个数学方程式,包括了x对时间的二阶导数,加上常数乘以x等于,还有一些限制条件。

麻省理工公开课 - 固态化学导论课程节选