Đáp án:
\(\begin{array}{l}
a.\\
{h_{\max }} = 25m\\
b.\\
{v_{\max }} = 10\sqrt 5 m/s\\
c.\\
v' = \sqrt {10} m/s
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\\
W = W'\\
{W_t} + {W_d} = mg{h_{\max }}\\
mgh + \frac{1}{2}m{v^2} = mg{h_{\max }}\\
{h_{\max }} = \frac{{gh + \frac{1}{2}{v^2}}}{g} = \frac{{10.5 + \frac{1}{2}{{.20}^2}}}{{10}} = 25m\\
b.\\
W' = W\\
mg{h_{\max }} = \frac{1}{2}m{v_{\max }}^2\\
{v_{\max }} = \sqrt {2g{h_{\max }}} = \sqrt {2.10.25} = 10\sqrt 5 m/s\\
c.\\
W' = W'\\
mg{h_{\max }} = mgh' + \frac{1}{2}mv{'^2}\\
v' = \sqrt {2(g{h_{\max }} - gh')} = \sqrt {2(10.25 - 10.3)} = \sqrt {10} m/s
\end{array}\)
