2-24 할리데이 11판 솔루션 일반물리학

$$\begin{cases} x&=20te^{-2t}\ut{m} \end{cases}$$ $$\begin{aligned} v&=\dxt{x}=\dt\(20te^{-2t}\)\\ &=20e^{-2t}(1-2t)=0\\ \end{aligned}$$ $$\therefore t=\frac{1}{2}\ut{s}$$ $$\begin{aligned} x(t)&=20te^{-2t}\ut{m},\\ \Ans&=x\(\frac{1}{2}\)\\ &=\frac{10}{e}\ut{m}\\ &\approx3.678794411714423\ut{m}\\ &\approx3.7\ut{m}\\ \end{aligned}$$