Đáp án:
\(\begin{array}{l}
a.\\
h = 4,05m\\
b.\\
W = 18,225J\\
c.\\
v = \sqrt {21} m/s\\
d.\\
h' = 2,25m
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\\
W = W'\\
\frac{1}{2}m{v^2} = mgh\\
\frac{1}{2}{.9^2} = 10.h\\
h = 4,05m\\
b.\\
W = W = \frac{1}{2}m{v^2} = \frac{1}{2}.0,{45.9^2} = 18,225J\\
c.\\
W = {W_t} + {W_d} = mgh + \frac{1}{2}mv{^2}\\
18,225 = 0,45.10.3 + \frac{1}{2}.0,45.v{^2}\\
v = \sqrt {21} m/s\\
d.\\
W = W' = mgh' + \frac{1}{2}mv'{^2}\\
18,225 = 0,45.10.h' + \frac{1}{2}.0,{45.6^2}\\
h' = 2,25m
\end{array}\)
