Đáp án:
\(\begin{array}{l}
29.\\
a.\\
v = 0,6m/s\\
b.\\
v = 1,3m/s\\
30.\\
a.\\
F = 86,6(N)\\
b.\\
F = 100(N)
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
29.\\
a.\\
p = p'\\
{m_1}{v_1} - {m_2}{v_2} = ({m_1} + {m_2})v\\
v = \frac{{{m_1}{v_1} - {m_2}{v_2}}}{{{m_1} + {m_2}}} = \frac{{38.1 - 2.7}}{{38 + 2}} = 0,6m/s\\
b.\\
p = p'\\
{m_1}{v_1} + {m_2}{v_2} = ({m_1} + {m_2})v\\
v = \frac{{{m_1}{v_1} + {m_2}{v_2}}}{{{m_1} + {m_2}}} = \frac{{38.1 + 2.7}}{{38 + 2}} = 1,3m/s\\
30.\\
a.\\
{M_F} = {M_P}\\
Fl = P\frac{l}{2}\cos {30^0} = > F = \frac{{P\sqrt 3 }}{4} = \frac{{200\sqrt 3 }}{4} = 86,6(N)\\
b.\\
{M_F} = {M_P}\\
Flcos300 = Pl2cos300 = > F = P2 = 100(N)
\end{array}\)
