2-59 할리데이 11판 솔루션 일반물리학

$$\begin{cases} t&=4.8\ut{s}\\ v_0&=0\\ v_1&=60\ut{km/h}=\frac{50}{3}\ut{m/s}\\ \end{cases}$$ $$\ab{a}$$ $$\begin{aligned} v&=v_0+at,\\ \frac{50}{3}&=0+a(4.8)\\ \end{aligned}$$ $$\begin{aligned} a&=\frac{125}{36}\ut{m/s^2}\\ &\approx 3.472222222222222\ut{m/s^2}\\ &\approx 3.5\ut{m/s^2}\\ \end{aligned}$$ $$\ab{b}$$ $$\begin{aligned} S&=\frac{1}{2}(v+v_0)t,\\ &=\frac{1}{2}\(\frac{50}{3}+0\)\cdot(4.8)\\ &=40\ut{m}\\ \end{aligned}$$ $$\ab{c}$$ $$\begin{aligned} S&=v_0t+\frac{1}{2}at^2,\\ 250&=(0)t+\frac{1}{2}\(\frac{125}{36}\)t^2\\ \end{aligned}$$ $$\begin{aligned} t&=12\ut{s} \end{aligned}$$