4-13 할리데이 10판 솔루션 일반물리학

$$\vec r=\i+3t^4\j+ t\k\ut{m}$$
(a) $$\begin{aligned} \vec v &= \dxt{\vec r}\\ &=\dt(\i+3t^4\j+ t\k)\\ &=12t^3\j+\k\ut{m/s}\\ \end{aligned}$$
(b) $$\begin{aligned} \vec a &= \dxt{\vec v}\\ &=\dt(12t^3\j+\k)\\ &=36t^2\j\ut{m/s^2}\\ \end{aligned}$$