The use of soft and flexible materials in technology, transport, and everyday life is well known. Mechanical properties such as slip and rolling friction play an important role in the manufacture of such objects. It appears as objects slide along each other. High friction is desirable in some objects, although high wear will be expected, in others, it is desirable to reduce friction. The study considers the possibility of experimentally determining some important mechanical properties of soft materials (textiles, elastomers). For this purpose, the forces of interaction between objects made of the same or different materials during their mutual motion are analyzed. From the analysis two physical parameters have been chosen as the estimation of the mechanical properties for the materials: the coefficient of sliding friction and the coefficient of rolling friction. For the identification of each parameter, the corresponding experimental rigs were dynamically studied. First, the oscillatory motion of a physical pendulum along an inclined plane with large angle of inclination, when the motion is damped by a constant sliding friction force, is studied. It is shown that by changing the initial conditions it is possible to synthesize a wide range of damped oscillations, from one half-cycle to five and more cycles. By measuring the angle at the starting position of the pendulum and the angle at the subsequent stopping position (after one oscillation cycle), an analytical formula for determining the coefficient of sliding friction was obtained. Then, the rolling friction coefficient was determined from the motion of the object along an inclined plane with a small angle of inclination. The moving object is designed as a platform on wheels. Two parameters were used to identify the rolling friction coefficient: the angle of inclination of the plane and the angle between the direction of motion of the object and the horizon. In addition, it has been shown that the rolling friction coefficient can also be determined with the above-mentioned physical pendulum rig. The results obtained in the work can also be used to identify the mechanical properties of non-soft materials. The main goal of the study is to obtain a theoretical justification for three new prototypes of experimental rigs for identifying the friction parameters of materials.