Đáp án:
a.Độ cao cực đại:
\[\frac{1}{2}m{v_o}^2 = mg{h_{\max }} \Rightarrow {h_{\max }} = \frac{{{v_o}^2}}{{2g}} = \frac{{{6^2}}}{{2.10}} = 1,8m\]
b.Bảo toàn cơ năng:
\[\begin{gathered}
{{\text{W}}_c} = {{\text{W}}_t} + {{\text{W}}_d} \hfill \\
\Leftrightarrow mg{h_{\max }} = {{\text{W}}_t} + 2{W_t} \hfill \\
\Leftrightarrow {\text{mg}}{{\text{h}}_{\max }} = 3mgh \hfill \\
\Leftrightarrow h = \frac{{{h_{\max }}}}{3} = 0,6m \hfill \\
\end{gathered} \]
c. Bảo toàn cơ năng:
\[\begin{gathered}
{{\text{W}}_c} = {{\text{W}}_t} + {{\text{W}}_d} \hfill \\
\Leftrightarrow \frac{1}{2}m{v_o}^2 = {{\text{W}}_d} + {{\text{W}}_d} = 2{W_d} \hfill \\
\Leftrightarrow \frac{1}{2}m{v_o}^2 = 2.\frac{1}{2}m{v^2} \hfill \\
\Leftrightarrow v = \frac{{{v_o}}}{{\sqrt 2 }} = 3\sqrt 2 m/s \hfill \\
\end{gathered} \]
