7-4 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} F&=2.0\ut{N}\\ m&=4.0\ut{kg}\\ \Delta d_x&=+1.0\ut{m} \end{cases} $$ $$ \begin{aligned} \Delta K&= W=\vec F \cdot \vec d\\ &=Fd\cos\theta\\ \end{aligned} $$ $$\ab{a,b}$$ $$ \begin{aligned} K&=K_0+\Delta K\\ \frac{1}{2}m{v_f}^2&=\frac{1}{2}m{v_0}^2+Fd\cos\theta\\ \end{aligned} $$ $$ \begin{aligned} v_f&=\sqrt{{v_0}^2+\frac{2Fd\cos\theta}{m}}\\ &=\sqrt{{v_0}^2+\cos\theta} \end{aligned} $$ $$\ab{a}$$ $$v_0=0,$$ $$v_f=\sqrt{\cos\theta}\ut{m/s}$$ $$\ab{b}$$ $$v_0=1.0\ut{m/s},$$ $$v_f=\sqrt{1+\cos\theta}\ut{m/s}$$ $$\ab{c}$$ $$ \begin{aligned} K&=K_0+\Delta K\\ \frac{1}{2}m{v_f}^2&=\frac{1}{2}m{v_0}^2-Fd\cos\theta\\ \end{aligned} $$ $$ \begin{aligned} v_f&=\sqrt{{v_0}^2-\frac{2Fd\cos\theta}{m}}\\ &=\sqrt{{v_0}^2-\cos\theta} \end{aligned} $$ $$v_0=1.0\ut{m/s},$$ $$v_f=\sqrt{1-\cos\theta}\ut{m/s}$$ $$\ab{d}$$ $$ \begin{cases} v_a=\sqrt{\cos\theta}\ut{m/s}\\ v_b=\sqrt{1+\cos\theta}\ut{m/s}\\ v_c=\sqrt{1-\cos\theta}\ut{m/s}\\ \end{cases} $$