A man fires a bullet of mass 50 g at a speed of 200 $\mathrm{m/s}$. The gun is of 5 kg mass. By what

Question

A man fires a bullet of mass 50 g at a speed of 200 $\mathrm{m/s}$. The gun is of 5 kg mass. By what velocity the gun rebounds backward?

Professor PC Thomas Classes · Answer

By conservation of momentum: $m_b v_b + m_g v_g = 0$. Here $m_b = 0.05 \mathrm{~kg}$, $v_b = 200 \mathrm{~m/s}$, $m_g = 5 \mathrm{~kg}$. $0.05 	imes 200 + 5 	imes v_g = 0 \implies 10 + 5v_g = 0 \implies v_g = -2 \mathrm{~m/s}$. The recoil speed is 2 m/s.