Đáp án:
\(\begin{array}{l}
8.C.16N\\
{F_2} - {F_1} < F < {F_1} + {F_2}\\
\Rightarrow 10 - 7 < F < 7 + 10\\
\Rightarrow 3 < F < 17\\
9.B.40000N\\
N = P - {F_{hd}} = mg - m\frac{{{v^2}}}{R}\\
= 5000.10 - 5000\dfrac{{{{10}^2}}}{{50}} = 40000N\\
10.C.50m/s\\
v = \sqrt {v_0^2 + 2gh} = \sqrt {{{40}^2} + 2.10.45} = 50m/s
\end{array}\)