  We present a relativistic formalism inspired on the Minkowski four-vectors
that also includes conservation laws such as the first law of thermodynamics.
It remains close to the relativistic four-vector formalism developed for a
single particle, but it is also related to the classical treatment of problems
that imperatively require both the Newton's second law and the energy
conservation law. We apply the developed formalism to inelastic collisions to
better show how it works.
