5-17 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} m&=89.0\ut{kg}\\ h&=1.50\ut{m}\\ d&=2.0\ut{cm}=2.0\times10^{-2}\ut{m}\\ g&=9.80665\ut{m/s^2} \end{cases} $$ $$ \begin{aligned} 2aS&=v^2-{v_0}^2,\\ 2(-g)(-H)&=v^2-{0}^2\\ v&=\sqrt{2gH} \end{aligned} $$ $$ \begin{cases} 2a_1S_1&={v_1}^2-{v_0}^2\\ 2a_2S_2&={v_2}^2-{v_1}^2\\ \end{cases} $$ $$ \begin{cases} 2(-g)(-h)&={v_1}^2-{0}^2\\ 2a(-d)&={0}^2-{v_1}^2\\ \end{cases} $$ $$\ab{a}$$ $$ \begin{aligned} a&=\frac{gh}{d}\\ &=75g\\ &=735.49875\ut{m/s^2}\\ &\approx 7.3\times10^2\ut{m/s^2} \end{aligned} $$ $$\ab{b}$$ $$\Sigma \vec F = m\vec a,$$ $$ \begin{aligned} \Sigma \vec F &= m\vec a\\ F_N-mg&=ma\\ F_N&=m(a+g)\\ &=6764g\\ &\approx 66332.18059999999\ut{N}\\ &\approx 66\ut{kN}\\ \end{aligned} $$