Conservation Law of Mass

Abstract

" Mass " is a basic property of a physical body which describes the amount of matter in it. In contrast to " weight " that is the force of gravitational attraction between an object and earth or some other astronomical body mass is not depending in the location of the body in space. We feel our weight while standing on the floor due to reaction of the floor on the bottom of our legs as dictated by Newton's third law, action = reaction, where the action is our weight. While mass cannot change under ordinary circumstances, weight changes dependent where the object is. In the classic mechanics of Newton (1643-1727) mass is defined as a measure to the persistence of a body, or as the degree of opposition of the body to a change in his motion (change in speed or direction). In other words, as a body mass is higher, his resistance to change in his motion is higher and the force needed for the change is higher. At about 1687 Newton provided also a working definitions for mass according to m = ρV, where the weight of the body on the surface of earth is simply the force acting between the body and the entire earth. However, the Austrian philosopher and physicist Ernst Mach (1838-1916) and other scientists preferred to define mass from Newton's second law m = F/a where force is either attraction or push while its source may be gravitation, electricity, magnetism, or the effort of muscles. Nowadays, it is accepted that mass is the amount of substance in a body, and more strictly the measure of its inertia, which is a property of the body that causes it to resist changes in the state of motion. An important fact about mass is as follows. About two hundred years scientists believed that Newton's approach was eternal, which assumed that mass was independent of its motion. And then came Einstein, and at the beginning of the twenty century presented his special relativity theory which led to the conclusion among others that the mass of a body increases with its speed according to m = m o [1 – (v/c) 2