4-28 할리데이 10판 솔루션 일반물리학

$$\begin{cases} \vec v_0 &= (42.0\ut{m/s},60.0\degree)\\ t &= 5.50\ut{s}\\ \vec a &= -g\j\\ g &\approx 9.80665\ut{m/s^2}\\ \end{cases}$$ $$\begin{aligned} \vec v_0 &= (42.0\ut{m/s},60.0\degree)\\ &=21\i+21\sqrt{3}\j\ut{m/s}\\ \end{aligned}$$
(a) $h=?$ $$\begin{aligned} \Delta y &= v_{y0}t+\frac{1}{2}at^2,\\ h &= \(21\sqrt{3}\)(5.50)+\frac{1}{2}(-g)(5.50)^2\\ &=\frac{231 }{2}\sqrt{3}-\frac{121 }{8}g\\ &\approx 51.7262870242\ut{m}\\ &\approx 51.7\ut{m}\\ \end{aligned}$$
(b) $H=?$ $$\begin{aligned} 2a\Delta y&=v_y^2-v_{y0}^2,\\ 2(-g)H&=(0)^2-\(21\sqrt{3}\)^2\\ H&=\frac{1323}{2 g}\\ &\approx67.4542274885\ut{m}\\ &\approx67.5\ut{m}\\ \end{aligned}$$