It is shown that motion is accompanied by energy and co-energy, which are inseparable. In a linear media they are equal and can replace each other. In a nonlinear media they are different, and each of them executes its own functions. Universal expression for co-energy of the physical system is offered. The concept of kinetic energy in variation principles does not fit. Examples refer to the electromagnetic field and relativistic theory of gravitation. The paradox of transversal and longitudinal relativistic masses is refuted.
- D. White and H. Woodson, Electromechanical energy conversion. Translated from of English, Leningrad, Russia: Energy, 1964. (Russian)
- A. Tchaban, Mathematic modeling of oscillation processes in electromechanical systems. Lviv, Ukraine: T. Soroka’s publishing house, 2008. (Ukrainian)
- V. Tchaban, Mathematical modeling in electrical engineering. Lviv, Ukraine: T. Soroka’s publishing house, 2010. (Ukrainian)
- R. P. Feynman, R. B. Leighton, and M. Sands The Feynman Lectures on Physics, vol. 1, 2. Translated from English, 1963. (Russian)
- V. Tchaban, “Kinetic co-energy of electromagnetic field”, Technical News, vol 37, no. 1, vol 38, no. 2, pp.59–60, 2013.(Ukrainian)
- V.Tchaban, “Symmetry of energy”, Computational Problems of Electrical Engineering, vol. 3, no. 1, pp. 115–119, 2013.
- V.Tchaban, “Relativistic co-energy”, Technical News, vol 37, no. 1, vol 38, no 2, pp. 11-13, 2013 (Ukrainian)