Đáp án:
$\begin{array}{l} {\rm{a}}{\rm{.}}{{\rm{W}}_{d0}} = 0\\ {{\rm{W}}_{t0}} = 1000\left( J \right)\\ {\rm{W}} = 1000\left( J \right) \end{array}$
b. $31,62 m/s$
c. $25m$
d. $22,36 m/s$
Giải thích các bước giải:
a. Vt thả vật
$\begin{array}{l}
v = 0 \Rightarrow {{\rm{W}}_{d0}} = 0\\
{{\rm{W}}_{t0}} = mg{h_0} = 2.10.50 = 1000\left( J \right)\\
{\rm{W}} = {{\rm{W}}_{t0}} + {{\rm{W}}_{d0}} = 1000\left( J \right)
\end{array}$
$\begin{array}{l}
b. \frac{1}{2}mv_{max}^2 = {\rm{W}}\\
\Rightarrow \frac{1}{2}.2.v_{max}^2 = 1000\\
\Rightarrow {v_{max}} = 31,62\left( {m/s} \right)\\
c. {{\rm{W}}_d} + {{\rm{W}}_t} = {\rm{W}}\\
{{\rm{W}}_d} = {{\rm{W}}_t} = \frac{{\rm{W}}}{2}\\
\Rightarrow mgh = \frac{{mg{h_0}}}{2}\\
\Rightarrow h = \frac{{{h_0}}}{2} = 25\left( m \right)\\
d. {{\rm{W}}_d} + {{\rm{W}}_t} = {\rm{W}}\\
{{\rm{W}}_d} = {{\rm{W}}_t} = \frac{{\rm{W}}}{2}\\
\Rightarrow \frac{1}{2}m{v^2} = \frac{{\frac{1}{2}mv_{max}^2}}{2}\\
\Rightarrow v = \frac{{{v_{max}}}}{{\sqrt 2 }} = 22,36\left( {m/s} \right)
\end{array}$
