8-66 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} \theta&=40\degree\\ m&=52\ut{kg}\\ v&=\Cons\\ S&=3.0\ut{m}\\ \mu&=0.35\\ g&=9.80665\ut{m/s^2} \end{cases} $$ $$ \put \begin{cases} \TE : \text{Thermal Energy}\\ \end{cases} $$ $$ \begin{cases} \Sigma F_x&=0\\ \Sigma F_y&=0\\ \end{cases} $$ $$ \begin{cases} F-f-mg\sin\theta&=0\\ N-mg\cos\theta&=0\\ \end{cases} $$ $$\ab{a}$$ $$ \begin{aligned} W&=FS\\ &=(mg\sin\theta+\mu mg\cos\theta)S\\ &=mgS(\sin\theta+\mu \cos\theta)\\ &\approx 1393.5337292560248\ut{J}\\ &\approx 1.4\times10^3\ut{J}\\ &\approx 1.4\ut{kJ}\\ \end{aligned} $$ $$\ab{b}$$ $$ \begin{aligned} \Delta \TE&=fS\\ &=\mu mgS\cos\theta\\ &\approx 410.1732037009548\ut{J}\\ &\approx 4.1\times10^2\ut{J}\\ \end{aligned} $$