From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m s-1 . Calculate the initial recoil velocity of the rifle.
Here we will use conservation of momentum :
Initial momentum of system ( rifle + bullet ) = Final momentum of system
The negative sign shows that velocity is opposite to that of the bullet. This is because the force on the rifle will be opposite by bullet (action-reaction pair).