Answer:
[tex]v = 0.478 m/s[/tex]
Explanation:
As we know that bullet strike the block and fix in it
so here if bullet and box is taken as a system then there is no external force on it
so here the initial momentum of bullet and block must be equal to final momentum of bullet and block
so here we have
[tex]m_1v_{1i} + m_2v_{2i} = m_1v + m_2v[/tex]
now we have
[tex]m_1 = 8 g[/tex]
[tex]v_1 = 120 m/s[/tex]
[tex]m_2 = 2kg[/tex]
[tex]v_{2i} = 0[/tex]
now from above equation we have
[tex](0.008)(120) + 2(0) = (0.008)v + 2v[/tex]
[tex]v = 0.478 m/s[/tex]