Suppose a system of two particles is known to obey the equations of motion: M(d2R/dt2 =∑i Fi(e) dL/dt = N(e) where R defines a point known as the center of mass and M = ∑i mi .From the equations of the motion of the individual particles show that the internal forces between particles satisfy both the weak and strong laws of action and reaction. The argument may be generalized to a system with arbitrary number of particles, thus proving the converse of the arguments leading to the above two equations.

Suppose a system of two particles is known to obey the equations of motion: M(d2R/dt2 =∑i Fi(e) dL/dt = N(e) where R defines a point known as the center of mass and M = ∑i mi .From the equations of the motion of the individual particles show that the internal forces between particles satisfy both the weak and strong laws of action and reaction. The argument may be generalized to a system with arbitrary number of particles, thus proving the converse of the arguments leading to the above two equations.