2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/141507In this paper we obtain a Hamilton-Jacobi theory for nonholonomic mechanical systems. The results are applied to a large class of nonholonomic mechanical systems, the so-called Čaplygin systems.13 pages, added references, fixed typos, comparison with previous approaches and some explanations added. To appear in J. Phys. AMathematical Physics70H20; 37J60; 70F25text