일반물리학 1 — Motion in Two and Three Dimensions: Problem 13

13 An object moves in such a way that its position (in meters) as a function of time (in seconds) is $\vec{r} = \hat{i} + 3t^2 \hat{j} + t \hat{k}$. Give expressions for (a) the velocity of the object and (b) the acceleration of the object as functions of time.