8-81 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} v_{A1}&=2.00\ut{m/s}\\ v_{B1}&=2.60\ut{m/s}\\ v_{A2}&=6.00\ut{m/s}\\ \end{cases} $$ $$\Sigma \Delta E=0,$$ $$\Delta \KE+\Delta \GE=0$$ $$ \begin{aligned} \Delta \(\frac{1}{2}m{v}^2\)&=-\Delta (mgy)\\ \Delta \({v}^2\)&=2g(-\Delta y)\\ {v_f}^2-{v_i}^2&=2g(-\Delta y)\\ &=\Cons\\ \end{aligned} $$ $${v_{B2}}^2-{v_{A2}}^2={v_{B1}}^2-{v_{A1}}^2$$ $$ \begin{aligned} v_{B2}&=\sqrt{{v_{A2}}^2+{v_{B1}}^2-{v_{A1}}^2}\\ &=\frac{\sqrt{969}}{5}\ut{m/s}\\ &\approx 6.2257529665093525\ut{m/s}\\ &\approx 6.23\ut{m/s}\\ \end{aligned} $$