2-10 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} v_{A0}&=60.0\ut{m/s}\\ v_{B0}&=\frac{3}{4}\cdot60.0\ut{m/s}=45.0\ut{m/s}\\ \Delta t_A&=5\ut{s}\\ \Delta t_B&=4\ut{s}\\ v_{A5}&=0\\ v_{B4}&=0\\ \Delta x_{A0\rarr B0}&=320\ut{m} \end{cases} $$ $$S=\frac{1}{2}(v+v_0)t,$$ $$ \begin{aligned} S_A&=\frac{1}{2}(v_{A5}+v_{A0})\Delta t_A\\ &=\frac{1}{2}(0+60.0\ut{m/s})(5\ut{s})\\ &=150\ut{m} \end{aligned} $$ $$ \begin{aligned} S_B&=\frac{1}{2}(v_{B4}+v_{B0})\Delta t_A\\ &=\frac{1}{2}(0+45.0\ut{m/s})(4\ut{s})\\ &=90.0\ut{m} \end{aligned} $$ $$ \begin{aligned} \Sigma S&=150\ut{m}+90\ut{m}\\ &=240\ut{m} \end{aligned} $$ $$ \begin{aligned} \Ans&=320\ut{m}-240\ut{m}\\ &=80.0\ut{m} \end{aligned} $$