2-68 할리데이 10판 솔루션 일반물리학

$$ v(40) =?$$ $$ \begin{aligned} \Ans &= \int_0^{\frac{40}{1000}}a\dd t\\ &= \int_{\frac{10}{1000}}^{\frac{20}{1000}}a\dd t+\int_{\frac{20}{1000}}^{\frac{30}{1000}}a\dd t+\int_{\frac{30}{1000}}^{\frac{40}{1000}}a\dd t\\ &=\frac{1}{2}\cdot0.01\cdot100+\frac{1}{2}\cdot0.01\cdot(100+400)+\frac{1}{2}\cdot0.01\cdot400\\ &=5\ut{m/s} \end{aligned} $$