Question

A 5.5-kg rifle fires an 11 g bullet with a velocity of 1000 m/s. Question: what is the recoil velocity of the rifle

Answer 1

From the conservation of momentum:

$m_1v_1+m_2v_2=0\to v_1=-\frac{m_2v_2}{m_1}=-\frac{0.011\cdot 1000}{5.5}=-2m/s$

Answer. $-2m/s$ in the opposite direction to the direction of motion of the bullet.