8-51 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} m&=1200\ut{kg}\\ v&=1.34\ut{m/s}\\ d_1&=\Delta x = 60\ut{m}\\ d_2&=\Delta y=30\ut{m}\\ \mu&=0.40\\ g&=9.80665\ut{m/s^2} \end{cases} $$ $$\tan\theta=\frac{d_2}{d_1}=\frac{1}{2}$$ $$\Sigma \vec F = 0\Harr \Delta \vec v=0,$$ $$ \begin{cases} \Sigma F_x&=0\\ \Sigma F_y&=0\\ \end{cases} $$ $$ \begin{cases} F-\mu N - mg\sin\theta&=0\\ N-mg\cos\theta&=0\\ \end{cases} $$ $$ \begin{aligned} F&=mg(\mu \cos\theta + \sin\theta)\\ &=mg(\mu \cos\theta + \sin\theta)\\ \end{aligned} $$ $$ \begin{aligned} P &= Fv\\ &=mgv(\mu \cos\theta + \sin\theta)\\ &=\frac{14472g}{5\sqrt5}\\ &\approx 12693.875161942688\ut{W}\\ &\approx 1.3\times10^4\ut{W}\\ &\approx 13\ut{kW}\\ \end{aligned} $$