7-33 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} \vec F_0&=-7.00\i+7.00\j+5.00\k\ut{N}\\ v_0&=5.00\ut{m/s}\\ m&=2.80\ut{kg}\\ \Delta \vec d&=4.00\i+4.00\j+7.00\k\ut{m} \end{cases} $$ $$W=\vec F \cdot \vec S=\Delta K,$$ $$K=\frac{1}{2}mv^2,$$ $$ \begin{aligned} K_1&=K_0+\vec F \cdot \vec S\\ \frac{1}{2}m{v_1}^2&= \frac{1}{2}m{v_0}^2+\vec F \cdot \vec S\\ {v_1}^2&= {v_0}^2+\frac{2\vec F \cdot \vec S}{m}\\ \end{aligned} $$ $$ \begin{aligned} v_1&=\sqrt{{v_0}^2+\frac{2\vec F \cdot \vec S}{m}}\\ &=5\sqrt2\ut{m/s}\\ &\approx 7.0710678118654755\ut{m/s}\\ &\approx 7.07\ut{m/s}\\ \end{aligned} $$