8-38 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} mg&=14720\ut{N}\\ v_i&=92.0\ut{km/h}=\frac{230}{9}\ut{m/s}\\ v_f&=0\\ f&=7022\ut{N}\\ g&=9.80665\ut{m/s^2} \end{cases} $$ $$ \put \begin{cases} \KE : \text{Kinetic Energy}\\ \TE : \text{Thermal Energy}\\ \end{cases} $$$$\Sigma \Delta E=0,$$ $$\Delta \KE+\Delta \TE=0$$ $$ \begin{aligned} \Delta \TE&=-\Delta \KE\\ fd&=-\Delta\(\frac{1}{2}mv^2\)\\ \end{aligned} $$ $$ \begin{aligned} d&=\frac{-m}{2f}\Delta\(v^2\)\\ &=\frac{-mg}{2fg}\({0}^2-{v_i}^2\)\\ &=\frac{mg{v_i}^2}{2fg}\\ &=\frac{194672000}{284391 g}\\ &\approx 69.80185540781503\ut{m}\\ &\approx 69.8\ut{m} \end{aligned} $$