Velocities, momenta, and energy distribution after impact can be calculated by a simple method. This technique can be used only when two bodies are involved that represent a closed system. One of the bodies is assumed to be at rest with respect to the chosen frame of reference before impact.
Very simple geometric figures are used with the method. For the central impact, for example, the distribution of velocity and momentum after impact is found from the point of intersection of two straight lines. One of these represents the ratio of masses of the interacting bodies, and the other represents the degree of elasticity (thus depending only on the ratio of the actual loss of translatory kinetic energy - resulting from impact - to the highest possible loss of translatory kinetic energy - resulting from a non-elastic impact between two bodies of the same mass and velocity.)