[en] The questions concerning the definition of generalized, true mechanical force and force work in special relativity are discussed. It is shown that the use of a 3-force leads to difficulties of the relativistic formulation of statics. Based on a 4-tensor of torque, the problems of equilibrium (e.g., for the Lewis-Tolman right-angled lever) and the dynamics of rigid body are discussed. For a continuous distribution of matter a 4-tensor of second rank of power-force and a 4-tensor of third rank of torque density as well as the Lagrangian covariant function are considered. It is shown that the application of center of mass is highly limited in relativistic mechanics; the notion of center of inertia is used instead of it