2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/36361We deduce from energy conservation a lower bound on the mass of any system capable of imparting a constant acceleration to a charged body. We also point out a connection between this bound and the so called dominant energy condition of general relativity.4 pages, plainTeX. New title, appendix added, small corrections and additions. Source for most up to date version: http://www.physics.syr.edu/~sorkinGeneral Relativity and Quantum CosmologyHigh Energy Physics - TheoryClassical Physicstext