Mechanics of the Free Mass Point

Abstract

The concept of the mass point is basic to the theory of mechanics. As we have already defined earlier (Sect. 1.4.1) we understand by the term ‘mass point’ a physical body of mass m but with negligible extension in all directions. One has to note that the concept of mass point does not necessarily presume small bodies. The term mass point is rather used for problems for which it is sufficient to observe only the behavior of one salient point of the macroscopic body, e.g. the center of gravity, without considering the movement of all the other points of the body. So it is to treat even the whole earth as a mass point if one is interested only in the path of the earth around the sun. That is obviously no longer allowed when we want to understand the origin of earth tides. We denote a mass point as free when it can react to the applied forces without being bound by any restraining condition.