6-6 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} mg&=140\ut{N}\\ \mu_s&=0.450\\ \mu_k&=0.320\\ g&=9.80665\ut{m/s^2} \end{cases} $$ $$\ab{a}$$ $$ \begin{aligned} F&=\mu_sF_N=\mu_smg\\ &=63.0\ut{N} \end{aligned} $$ $$\ab{b}$$ $$ \begin{aligned} F&=\mu_kF_N=\mu_kmg\\ &=\frac{224}{5}\ut{N}\\ &=44.8\ut{N} \end{aligned} $$ $$\ab{c}$$ $$\Sigma \vec F = m\vec a,$$ $$ \begin{aligned} a&=\frac{F}{m}\\ &=\frac{\mu_smg}{m}\\ &=\mu_sg\\ &=4.4129925\ut{m/s^2}\\ &\approx 4.41\ut{m/s^2}\\ \end{aligned} $$