2-28 할리데이 11판 솔루션 일반물리학

$$\begin{cases} \Delta x_A &=700\ut{m}\\ \Delta x_B &=700\ut{m}\\ a_A &= 1.2\ut{m/s^2}\\ a_B &= -1.2\ut{m/s^2} \end{cases}$$ $$\ab{a}$$ $$\begin{aligned} S&=v_0t+\frac{1}{2}at^2,\\ 700&=(0)t+\frac{1}{2}(1.2)t^2\\ \end{aligned}$$ $$t_A=10 \sqrt{\frac{35}{3}}\ut{s}$$ $$t_A=t_B,$$ $$\begin{aligned} \Sigma t &= 2t_A\\ &=20 \sqrt{\frac{35}{3}}\ut{s}\\ &\approx68.31300510639733\ut{s}\\ &\approx68\ut{s} \end{aligned}$$ $$\ab{b}$$ $$\begin{aligned} 2aS&=v^2-v_0^2,\\ 2(1.2)(700)&=v^2-(0)^2\\ \end{aligned}$$ $$\begin{aligned} v&=4 \sqrt{105}\ut{m/s}\\ &\approx40.98780306383839\ut{m/s}\\ &\approx41\ut{m/s} \end{aligned}$$