Resumen
Basing on Mach?s principle we can assume the reality of inertial forces, also called fictitious forces. In this research paper we present the ideas of Mach in the historical context of the criticism directed to the Newtonian nation of absolute space, and an analysis of Newton?s First Law, usually accepted without further discussions in the teaching of mechanics. We show next how those ideas can be largely implemented by relational mechanics, in which forces are interpreted as resulting from the interaction of local masses with the distant matter in the universe. In the conclusion, we have considered some implications for teaching.