Đáp án:
\(\begin{array}{l}
15.\\
a.\\
a = - 30m/{s^2}\\
{F_h} = 120000N\\
b.\\
t = \frac{2}{3}s\\
16.\\
a.\\
\Delta {W_d} = - 40000000J\\
b.\\
{F_h} = - 250000N\\
P = 333333,333W
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
15.\\
a.\\
a = \frac{{{v^2} - v_0^2}}{{2s}} = \frac{{{{10}^2} - {{20}^2}}}{{2.50}} = - 30m/{s^2}\\
{F_h} = - ma = - 4000. - 30 = 120000N\\
b.\\
a = \frac{{v' - v}}{t}\\
t = \frac{{v' - v}}{a} = \frac{{0 - 20}}{{ - 30}} = \frac{2}{3}s\\
16.\\
a.\\
\Delta {W_d} = {W_d}' - {W_d} = \frac{1}{2}mv{'^2} - \frac{1}{2}m{v^2} = 0 - \frac{1}{2}{.200000.20^2} = - 40000000J\\
b.\\
{F_h} = \frac{{\Delta {W_d}}}{s} = \frac{{ - 40000000}}{{160}} = - 250000N\\
P = \frac{{|\Delta {W_d}|}}{t} = \frac{{40000000}}{{2.60}} = 333333,333W
\end{array}\)
