4-17 할리데이 10판 솔루션 일반물리학

$$\begin{cases} \vec a&=6.0\i-3.0\j\ut{m/s^2}\\ \vec v_0&=12.0\i+18.0\j\ut{m/s}\\ \end{cases}$$ $$\begin{aligned} \vec v&=\vec v_0+\vec a t\\ &=12.0\i+18.0\j+(6.0\i-3.0\j)t\ut{m/s}\\ &=(12.0+6.0t)\i+(18.0-3.0t)\j\ut{m/s}\\ \end{aligned}$$ $$v_y=18.0-3.0t=0$$ $$t=6\ut{s}$$ $$\begin{aligned} \vec v_6&=(12.0+6.0\cdot6)\i+(18.0-3.0\cdot6)\j\ut{m/s}\\ &=48\i\ut{m/s} \end{aligned}$$