6-27 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} mg&=22\ut{N}\\ F_N&=70\ut{N}\\ \mu_s&=0.60\\ \mu_k&=0.40\\ \end{cases} $$ $$ \begin{aligned} f_s&=\mu_sF_N\\ &=42\ut{N} \end{aligned} $$ $$ \begin{aligned} f_k&=\mu_kF_N\\ &=28\ut{N} \end{aligned} $$ $$\ab{a}$$ $$P=+34\ut{N}$$ $$ \begin{aligned} \abs{\Sigma F_y}&=\abs{P-mg}\\ &=\abs{12\ut{N}}\lt f_s=42\ut{N},\\ f&=\Sigma F_y=-12\ut{N},\text{Down} \end{aligned} $$ $$\ab{b}$$ $$P=+12\ut{N}$$ $$ \begin{aligned} \Sigma F_y&=P-mg\\ &=\abs{-10\ut{N}}\lt f_s=42\ut{N},\\ f&=-\Sigma F_y=10\ut{N},\text{Up} \end{aligned} $$ $$\ab{c}$$ $$P=+48\ut{N}$$ $$ \begin{aligned} \Sigma F_y&=P-mg\\ &=\abs{26\ut{N}}\lt f_s=42\ut{N},\\ f&=-\Sigma F_y=-26\ut{N},\text{Down} \end{aligned} $$ $$\ab{d}$$ $$P=+70\ut{N}$$ $$ \begin{aligned} \Sigma F_y&=P-mg\\ &=\abs{48\ut{N}}\gt f_s=42\ut{N},\\ f&=-f_k=-28\ut{N},\text{Down} \end{aligned} $$ $$\ab{e}$$ $$P=-10\ut{N}$$ $$ \begin{aligned} \Sigma F_y&=P-mg\\ &=\abs{-32\ut{N}}\lt f_s=42\ut{N},\\ f&=-\Sigma F_y=32\ut{N},\text{Up} \end{aligned} $$ $$\ab{f}$$ $$P=-22\ut{N}$$ $$ \begin{aligned} \Sigma F_y&=P-mg\\ &=\abs{-44\ut{N}}\gt f_s=42\ut{N},\\ f&=f_k=28\ut{N},\text{Up} \end{aligned} $$ $$\ab{g}$$ $$\text{d}$$ $$\ab{h}$$ $$\text{f}$$ $$\ab{i}$$ $$\text{a,c,d}$$