2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33966Variational principle for a solid in classical mechanics is formulated in terms of a thin elastic 4D bar strain in Minkowsky events space of special relativity. It is shown, that the sum of elastic 4-energies of weak twist and bending under some identifications takes the form of classical non-relativistic action for a solids dynamics. The necessary conditions on 4D bar parameters and elastic constants, providing validity of Newton mechanics, are found.Latex 2e, 23 pages, 4 figures, talk at Ulyanovsk school-seminar 2000. Accepted for printing in Nuovo Cimento BGeneral Relativity and Quantum Cosmologytext