4-55 할리데이 11판 솔루션 일반물리학

$$\begin{cases} v&=8.50\ut{m/s}\\ a_R&=4.00\ut{m/s^2}\\ \end{cases}$$ $$\ab{a}$$ $$a_R=\frac{v^2}{R},$$ $$\begin{aligned} R&=\frac{v^2}{a_R}\\ &=\frac{289}{16}\ut{m}\\ &=18.0625\ut{m}\\ &\approx 18.1\ut{m}\\ \end{aligned}$$ $$\ab{b}$$ $$v=\frac{2\pi R}{T},$$ $$\begin{aligned} T&=\frac{2\pi R}{v}\\ &=\frac{17\pi}{4}\ut{s}\\ &\approx 13.35176877775662\ut{s}\\ &\approx 13.4\ut{s}\\ \end{aligned}$$