Mass

Weight. Unit of measurement of the International System, so-called MKS, whose fundamental units are: Meter (M), Kilogram (K), Second (S). According to this system, in which the force is a derived unit and expressed in Newton (N), the mass-kg must be used instead of the weight-kg, in expressing the characteristic of “mass” instead of “force” when indicating the quantity of matter in the bodies. In fact, the weight-kg was just a traditional measurement system (so-called technical) that used the kg-force as a fundamental unit, and the mass as a derived unit (equal to the weight divided by the acceleration of gravity). Among the limitations of the technical system (also known as the engineers’) there are the differences that this assumes in the various countries, particularly in the Anglo-Saxon world, which use non-decimal units of measurement (foot, etc …) as well as the non-absolute reference acceleration of terrestrial gravity, in defining the same kg-force. However, since the value of the kg-mass, expressed in the SI system, is numerically equal to the value of the kg-weight, expressed in the technical system, no practical difficulties are encountered in the transition to the SI system. The use of Mass as a unit of measurement in railways was consequently incorporated in legislative texts. In particular, we will talk about train mass and braking mass instead of the traditional weight and braked weight. For further clarification, the following example applies: in the technical system, a “weight” train of 1,000,000 kg has a mass of approx. 101,937 kg-m (in this case kg-m was a unit otherwise called “bes” or “inerta”); in the SI system, the same train has a “mass” of 1,000,000 kg and a weight of 9,810,000 Newton, or otherwise expressed as a multiple of 981,000 daN (deca Newton). The use of the value of the acceleration of gravity (9.81 m / s2) is recognized in the transformations