9-44 할리데이 11판 솔루션 일반물리학

$$\put \begin{cases} m:\text{man}\\ c:\text{car}\\ \end{cases} $$ $$ \begin{cases} m_mg&=850\ut{N}\\ m_cg&=1700\ut{N}\\ v_{ci}&=18.2\ut{m/s}\\ v_{m\larr c}&=-4.00\ut{m/s} \end{cases} $$ $$ \begin{aligned} v_{m\larr c}&=v_m-v_c \end{aligned} $$ $$\Delta \Sigma \vec p=0,$$ $$\vec p_i=\vec p_{mf}+\vec p_{cf}$$ $$(m_m+m_c)v_i=m_mv_m+m_cv_c$$ $$ v_c=v_i-\frac{m_m }{m_c+m_m}v_{m\larr c}$$ $$ \begin{aligned} \Delta v_c&=v_c-v_i\\ &=-\frac{m_m }{m_c+m_m}v_{m\larr c}\\ &=-\frac{m_m g}{m_cg+m_mg}v_{m\larr c}\\ &=\frac{4}{3}\ut{m/s}\\ &\approx 1.3333333333333333\ut{m/s}\\ &\approx 1.33\ut{m/s}\\ \end{aligned} $$