. What is Conservation of Linear momentum
If net external force acting on a particle or system is zero then net linear momentum of the particle or the system remains constant. This is called conservation of linear momentum.
Depending upon forces acting on a system, linear momentum might be conserved in one direction ( i.e. px = 0) or two directions ( i.e. px = 0, py = 0) or in all directions (i.e. px = 0, py = 0, pz = 0 ). If a component of the net external force on a closed system is zero along an axis, then the component of the linear momentum of the system along that axis cannot change.