The beginning of the first phase is considered from the moment the bodies are contacted, the end of the phase is taken at the time of a decrease in the relative speed to zero. The time interval between the beginning of the first phase and its end is equal to half the duration of the blow 2. The onset of the second phase is characterized by the removal of each other of the collapsing bodies, a decrease in the deformation and the restoration of the previous form. Relative speed, changing the sign, increases in absolute value; finally
