6-46 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} T&=30\ut{s}\\ R&=4.0\ut{m}\\ \end{cases} $$ $$\ab{a}$$ $$ \begin{aligned} v&=\frac{2\pi R}{T}\\ &=\frac{4\pi}{15}\\ &\approx 0.8377580409572781\ut{m/s}\\ &\approx 0.84\ut{m/s}\\ \end{aligned} $$ $$\ab{b}$$ $$\Sigma F_R = \frac{mv^2}{R},$$ $$\mu F_N=\mu m g=\frac{mv^2}{R}$$ $$ \begin{aligned} \mu &=\frac{v^2}{gR}\\ &=\frac{4\pi^2 R}{g T^2}\\ &=\frac{4\pi^2}{225g}\\ &=0.017891903330611796\\ &=0.018\\ \end{aligned} $$