4-39 할리데이 11판 솔루션 일반물리학

$$\begin{cases} \vec v_0&=4.50\i\ut{m/s}\\ \vec a&=1.2\j\ut{m/s^2}\\ t&=4.70\ut{s} \end{cases}$$ $$\begin{aligned} \vec v(t)&=\vec v_0+\Delta \vec v\\ &=\vec v_0+\int_0^{t}\vec a\dd t\\ &=4.50\i+\int_0^{t}1.2\j\dd t\\ &=4.50\i+1.2t\j\\ \end{aligned}$$ $$\ab{a}$$ $$\begin{aligned} \vec v(4.70)&=4.50\i+1.2(4.7)\j\ut{m/s}\\ &=4.50\i+5.64\j\ut{m/s}\\ &\approx 4.5\i+5.6\j\ut{m/s}\\ \end{aligned}$$ $$\ab{b}$$ $$\begin{aligned} \vec r&=\vec r_0+\Delta r\\ &=0+\int_0^{t}\vec v\dd t\\ &=\int_0^{t}\(4.50\i+1.2t\j\)\dd t\\ &=4.5t\i+0.6t^2\j \end{aligned}$$ $$\begin{aligned} \vec r(4.70)&=21.15\i+13.254\j\ut{m}\\ &\approx 21\i+13\j\ut{m}\\ \end{aligned}$$