6-17 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} \theta&=40\degree\\ x&=\theta-\phi\\ \mu_s&=0.60\\ \end{cases} $$ $$ \begin{aligned} \Sigma F_y&=F_N-mg\cos x=0\\ F_N&=mg\cos x \end{aligned} $$ $$ \begin{aligned} \Sigma F_x&=\mu_sF_N - mg\sin x=0\\ &=\mu_smg\cos x- mg\sin x\\ \end{aligned} $$ $$\mu_s=\tan x$$ $$ \begin{aligned} \phi&=40\degree-\tan^{-1}\(\frac{3}{5}\)\\ &\approx 0.15771220052714763\ut{rad}\\ &\approx 0.16\ut{rad}\\ \end{aligned} $$