8-78 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} v_i&=7.0\ut{m/s}\\ h&=2.0\ut{m}\\ \mu&=0.50\\ \end{cases} $$ $$ \put \begin{cases} \KE : \text{Kinetic Energy}\\ \GE : \text{Gravitational Potential Energy}\\ \TE : \text{Thermal Energy}\\ \end{cases} $$ $$\Sigma \Delta E=0,$$ $$\Delta \KE+\Delta \GE+\Delta \TE=0$$ $$ \begin{aligned} \Delta \TE&=-\Delta \KE-\Delta \GE\\ fd&=-\Delta\(\frac{1}{2}mv^2\)-\Delta (mgy)\\ \mu m g d&=-\frac{1}{2}m\Delta\(v^2\)-mg\Delta y\\ \mu g d&=\frac{1}{2}\({v_i}^2-{v_f}^2\)-g\Delta y\\ &=\frac{1}{2}{v_i}^2-g\Delta y\\ \end{aligned} $$ $$ \begin{aligned} d&=\frac{{v_i}^2}{2\mu g}-\frac{\Delta y}{\mu}\\ &=\frac{49}{g}-4\\ &\approx 0.9966094435918484\ut{m}\\ &\approx 1.0\ut{m}\\ \end{aligned} $$