ABSTRACT
In the course of studying mechanical phenomena a number of concepts are introduced, for example, energy, velocity, stress, etc., which characterize the considered phenomenon and can be specified and determined with the help of numbers. All the questions concerning motion and equilibrium can be formulated as problems for determining certain functions and numerical values for the quantities characterizing the phenomenon. It is necessary to go to the root of the matter and give a general qualitative analysis in order to conduct and process experiments, the results of which would have allowed one to determine general laws and would have been applied to the cases when the experiment was not used directly. Dimensional and similarity theory provides one with the possibility of such prior qualitative-theoretical analysis and the choice of a set for characteristic dimensionless parameters. Quantities whose values depend on accepted scales, that is, on a system of units of measurement, are referred to as dimensional or concrete quantities.
