4-37 할리데이 10판 솔루션 일반물리학

$$\begin{cases} y_0 &= 12\ut{m}\\ v_x &= 2.50\ut{m/s}\\ \end{cases}$$ $$\begin{cases} \vec a &=-g\j\\ g &\approx 9.80665\ut{m/s^2}\\ \end{cases}$$ $$\begin{cases} t_0 : \text{Start}\\ t_1=0.900\ut{sec}\\ t_2 : \text{Finish}\\ \end{cases}$$
(a) $\Delta x_1=?$ $$\begin{aligned} \Delta x &= v_xt,\\ &=2.25\ut{m} \end{aligned}$$
(b) $y_1=?$ $$\begin{aligned} S&=v_0t+\frac{1}{2}at^2,\\ \Delta y &= v_{y0}t-\frac{1}{2}gt^2\\ &=-\frac{1}{2}gt^2 \end{aligned}$$ $$\begin{aligned} y_1&=y_0+\Delta y,\\ &=y_0-\frac{1}{2}gt^2\\ &=12-\frac{81 g}{200}\\ &\approx 8.02830675\ut{m}\\ &\approx 8.03\ut{m}\\ \end{aligned}$$
(c) $\Delta x_2=?$ $$\begin{aligned} S&=v_0t+\frac{1}{2}at^2,\\ -y_0&=-\frac{1}{2}gt^2\\ \end{aligned}$$ $$ t=2\sqrt{\frac{6}{g}}$$ $$\begin{aligned} \Delta x &= v_x t,\\ &= 5\sqrt{\frac{6}{g}}\\ &\approx 3.910977268492994\ut{m}\\ &\approx 3.91\ut{m}\\ \end{aligned}$$