2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/209302We present a thought experiment that involves a high sensitivity balance initially in a state of mechanical equilibrium but not in a state of thermal equilibrium. After reaching the state of thermal equilibrium it is no longer in a state of mechanical equilibrium.General PhysicsIllustrating delta(E)=c^2 delta(m)text