Đáp án:
\(\begin{array}{l}
a.\\
W = 7,2J\\
b.\\
{h_{\max }} = 3,6m\\
c.\\
h' = 1,8m\\
d.\\
h = 0,6m
\end{array}\)
\(v = 2\sqrt {12} m/s\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\\
W = {W_t} + {W_d} = mgh + \frac{1}{2}m{v^2} = 0,2.10.1,8 + \frac{1}{2}.0,{2.6^2} = 7,2J\\
b.\\
W = {W_{t\max }} = mg{h_{\max }}\\
7,2 = 0,2.10.{h_{\max }}\\
{h_{\max }} = 3,6m\\
c.\\
W' = {W_t}' + {W_d}' = 2{W_t}' = 2mgh'\\
7,2 = 2.0,2.10.h'\\
h' = 1,8m\\
d.\\
W = {W_t} + {W_d}5{W_t} + {W_t} = 6{W_t} = 6mgh\\
7,2 = 6.0,2.10.h\\
h = 0,6m
\end{array}\)
\(\begin{array}{l}
{W_d} = 5{W_t}\\
\frac{1}{2}m{v^2} = 5mgh\\
\frac{1}{2}.{v^2} = 5.10.0,6\\
v = 2\sqrt {12} m/s
\end{array}\)