EN
A necessity to obtain numeral data about variability of a mass connected with the working element became an inspiration for the research. Such a need results from the fact that a variance of material coordinates is not a zero, which indicates variability of the mass in motion. Such data is necessary when an equation of motion in its proper form is constructed. Such equations, taking into consideration mass variability, are written as a dependence for forces, moments (because of additional degrees of freedom) and also further densities resulting from weak, integral laws of conservation. The problem has been discussed for the case of a flat cycloidal motion.