2-7 할리데이 10판 솔루션 일반물리학

$$ \begin{aligned} & \begin{cases} S_0 &= 40\ut{km} \\ \abs{v_{\text{BIRD}}} &= 36\ut{km/h} \\ v_A &= 16\ut{km/h} \\ v_B &= -25\ut{km/h} \end{cases}\\ \end{aligned} $$
(a) $$ \begin{aligned} \\ \Ans &= \Sigma\abs{S_{\text{BIRD}}} = ? \\ &= \Sigma\abs{v_{\text{BIRD}} \cdot t_{\text{BIRD}}} \\ &=\abs{v_{\text{BIRD}}}\cdot \Sigma\abs{t_{\text{BIRD}}} \\ &=\abs{v_{\text{BIRD}}}\cdot t_{\text{CARCRASH}} \\ &= \abs{v_{\text{BIRD}}}\cdot \frac{S_0}{v_A-v_B} \\ &= 36\ut{km/h}\cdot \frac{40\ut{km}}{16\ut{km/h}-(-25\ut{km/h})} \\ &= 36\ut{km/h}\cdot \frac{40}{41}\ut{h} \cdots (2-7-1) \\ &= \frac{1440}{41}\ut{km} \\ &\approx 35.121951219512195122\ut{km} \\ &\approx 35\ut{km} \end{aligned} $$
(b) $$ \begin{aligned} \\ \Ans &= \Delta x_{\text{BIRD}} = ? \\ &= x_{\text{BIRD}2} - x_{\text{BIRD}1} \\ &= x_{A2} - x_{A1} \\ &= \Delta x_A \\ &= v_At_{\text{CARCRASH}} \\ &= 16\ut{km/h}\cdot \frac{40}{41}\ut{h} \because(2-7-1) \\ &= \frac{640}{41}\ut{km} \\ &\approx 15.609756097560975610\ut{km} \\ &\approx 16\ut{km} \end{aligned} $$