Đáp án:
\(\begin{array}{l}
{A_C} = - \frac{{2000000}}{9}J\\
{A_F} = 567901,2346J
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
\\
v = 18km/h = 5m/s\\
v' = 46km/h = \frac{{115}}{9}m/s\\
a = \frac{{v' - v}}{t} = \frac{{\frac{{115}}{9} - 5}}{{10}} = \frac{7}{9}m/{s^2}\\
s = \frac{{v{'^2} - {v^2}}}{{2a}} = \frac{{{{\frac{{115}}{9}}^2} - {5^2}}}{{2.\frac{7}{9}}} = \frac{{800}}{9}m\\
{F_{ms}} = \mu mg = 0,05.5000.10 = 2500N\\
{A_C} = {F_{ms}}.s.\cos 180 = 2500.\frac{{800}}{9}.\cos 180 = - \frac{{2000000}}{9}J\\
{W_d}' - {W_d} = {A_F} + {A_c}\\
\frac{1}{2}mv{'^2} - \frac{1}{2}m{v^2} = {A_F} - \frac{{2000000}}{9}\\
\frac{1}{2}.5000.{\frac{{115}}{9}^2} - \frac{1}{2}{.5000.5^2} = {A_F} - \frac{{2000000}}{9}\\
\Rightarrow {A_F} = 567901,2346J
\end{array}\)
