2-7 할리데이 11판 솔루션 일반물리학

$$\ab{a}$$ $$\begin{aligned} x_5&=x_0+\Delta x_{0\rarr5} \\ &=0+\int_0^5 v\dd t \\ &=\frac{1}{2}(2\ut{s}+4\ut{s})8\ut{m/s}+\frac{1}{2}(4\ut{m/s}+8\ut{m/s})1\ut{s}\\ &=30\ut{m} \end{aligned}$$ $$\ab{b}$$ $$v_5=4\ut{m/s}$$ $$\ab{c}$$ $$\begin{aligned} a_5&=\dt v\\ &=\frac{-8\ut{m/s}}{2\ut{s}}\\ &=-4\ut{m/s^2} \end{aligned}$$ $$\ab{d}$$ $$\begin{aligned} \bar{v}_{1\rarr5}&=\frac{\Delta x_{1\rarr5}}{5-1}\\ &=\frac{\Delta x_{0\rarr5}-\Delta x_{0\rarr1}}{4}\\ &=\frac{30-\frac{1}{2}\cdot1\cdot4}{4}\\ &=7\ut{m/s} \end{aligned}$$ $$\ab{e}$$ $$\begin{aligned} \bar{a}_{1\rarr5}&=\frac{v_5-v_1}{5-1}\\ &=\frac{4\ut{m/s}-4\ut{m/s}}{4}\\ &=0 \end{aligned}$$