Đáp án:
\(\begin{array}{l}
a.\\
{v_2} = 3,43m/s\\
b.\\
{v_2} = 5,14m/s
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\\
p = p'\\
({m_1} + {m_2})v = {m_1}{v_1} + {m_2}{v_2}\\
{v_2} = \frac{{({m_1} + {m_2})v - {m_1}{v_1}}}{{{m_2}}} = \frac{{(60 + 140)3 - 60.2}}{{140}} = 3,43m/s\\
b.\\
p = p'\\
({m_1} + {m_2})v = - {m_1}{v_1} + {m_2}{v_2}\\
{v_2} = \frac{{({m_1} + {m_2})v + {m_1}{v_1}}}{{{m_2}}} = \frac{{(60 + 140)3 + 60.2}}{{140}} = 5,14m/s
\end{array}\)