let's assume that there are two ball of identical mass and one of the two is stationary . and the collision is NOT head on . I know that the law of restitution always applies ONLY to the line of impact of two bodies .What about momentum , is it conserved in both the line of impact AND the line perpendicular to it ? I am asking because i feel like the law of restitution is similar to momentum conservation so i feel like applying it "twice". Is momentum conserved in all axes regardless of whether 0≤e≤1 ? Thank you !