4-21 할리데이 10판 솔루션 일반물리학

$$\begin{cases} \vec v_0 &= 6.75\i\ut{m/s}\\ \Delta \vec r &= -5.00\j\ut{cm}\\ \vec a &= -g\j\\ g &\approx 9.80665\ut{m/s^2}\\ \end{cases}$$ $$\Delta x =?$$ $$\begin{aligned} \Delta y &= v_{y0}t+\frac{1}{2}a_yt^2,\\ -5.00\times10^{-2} &= 0\cdot t+\frac{1}{2}(-g)t^2\\ 5.00\times10^{-2} &= \frac{1}{2}gt^2\\ t&= \frac{1}{\sqrt{10g}} \end{aligned}$$ $$\begin{aligned} \Delta x &= v_x t = v_0 t\\ &= \frac{6.75}{\sqrt{10g}}\\ &= \frac{27}{4\sqrt{10g}}\\ &\approx \frac{27}{4\sqrt{10\cdot 9.80665}}\ut{m}\\ &\approx 0.681621742272\ut{m}\\ &\approx 0.682\ut{m}\\ \end{aligned}$$