9-11 할리데이 11판 솔루션 일반물리학

$$\begin{cases} m&=4.0\ut{g}=4.0\times10^{-3}\ut{kg}\\ f&=120\ut{/min}\\ \vec v_i&=500\ut{m/s}\\ \vec v_f&=-\vec v_i=-500\ut{m/s}\\ \end{cases}$$ $$\begin{aligned} T&=\frac{1}{f}\\ &=\frac{1\ut{min}}{120}\\ &=\frac{1}{2}\ut{s} \end{aligned}$$ $$\vec J=\Delta \vec P,$$ $$F\Delta t=m\Delta \vec v$$ $$\begin{aligned} \vec F&=\frac{m(\vec v_f-\vec v_i)}{T}\\ &=-\frac{2m\vec v_i}{T}\\ &=-8\ut{N}\\ \end{aligned}$$ $$F=8.0\ut{N}$$