Question

11. The expanding gases that leave the muzzle of a rifle also contribute to
the recoil. A 30-caliber bullet has mass 0.00720 kg and a speed of 601
m/s relative to the muzzle when fired from a rifle that has mass 2.80
kg. The loosely held rifle recoils at a speed of 1.85 m/s relative to the
earth. Find the momentum of the propellant gases in a coordinate
system attached to the earth as they leave the muzzle of the rifle

Answer 1

The momentum of the propellant gases in a coordinate system attached to the earth as they leave the muzzle of the rifle is

$$p=mv=0.0072·601=4.33\text{ kg m/s}.$$