9-53 할리데이 11판 솔루션 일반물리학

$$\begin{cases} m_A&=80\ut{kg}\\ m_B&=320\ut{kg}\\ v_{i}&=0\\ v_{A\larr B}&=2.5\ut{m/s}\\ M&=m_A+m_B=400\ut{kg}\\ \end{cases}$$ $$\Delta \Sigma \vec p=0,$$ $$\begin{cases} 0&=m_Av_A+m_Bv_B\\ v_{A\larr B}&=v_A-v_B,\\ \end{cases}$$ $$\begin{aligned} v_B&=-\frac{m_A}{M}v_{A\larr B}\\ &=-\frac{1}{2}\ut{m/s}\\ &=-0.5\ut{m/s}\\ \end{aligned}$$ $$\ab{a}$$ $$\text{Dpwn}$$ $$\ab{b}$$ $$v_B=0.5\ut{m/s}$$ $$\ab{c}$$ $$\Delta \Sigma \vec p=0,$$ $$v_B=0$$