5-55 할리데이 11판 솔루션 일반물리학

$$\begin{cases} m&=5.0\times10^4\ut{kg}\\ g&=9.80665\ut{m/s^2} \end{cases}$$ $$\ab{a}$$ $$\Sigma \vec F = 0 \Harr \Delta \vec v=0,$$ $$\begin{aligned} \Sigma F &= F-mg= 0\\ F&=mg\\ &=\frac{980665}{2}\ut{N}\\ &=490332.5\ut{N}\\ &\approx 4.9\times10^5\ut{N} \end{aligned}$$ $$\ab{b}$$ $$\Sigma \vec F = m\vec a,$$ $$\begin{aligned} F-mg &= m a\\ F&=m(a+g)\\ &=\frac{2980665}{2}\ut{N}\\ &=1490332.5\ut{N}\\ &\approx 1.5\times10^6\ut{N}\\ &\approx 1.5\ut{MN}\\ \end{aligned}$$