2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/185878We prove that when the bag surface is allowed to move radially, the equations of motion derived from the MIT bag Lagrangian with massless quarks and a spherical boundary admit only one solution, which corresponds to a bag expanding at the speed of light. This result implies that some new physics ingredients, such as coupling to meson fields, are needed to make the dynamical bag a consistent model of hadrons.Revtex, no figures. Submitted to Journal of Physics ANuclear TheoryMathematical Physicstext