Đáp án:
\(\begin{array}{l}
a.\\
{v_0} = 30m/s\\
b.\\
{v_B} = 8\sqrt {10} m/s
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\\
W = {W_A}\\
mgh + \frac{1}{2}m{v_0}^2 = mg{h_A}\\
10.3 + \frac{1}{2}.v_0^2 = 10.48\\
{v_0} = 30m/s\\
b.\\
{W_B} = {W_{dB}} + {W_{tB}} = {W_{dB}} + \frac{1}{2}{W_{dB}} = \frac{3}{2}{W_{dB}}\\
mg{h_B} = \frac{3}{2}.\frac{1}{2}mv_B^2\\
10.48 = \frac{3}{4}.{v_B}^2\\
{v_B} = 8\sqrt {10} m/s
\end{array}\)