2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/137144The Lorentz transformation is entirely derived from length contraction, itself established through the known light-clock thought experiment . This makes the derivation accessible to beginning students once Eintein's two postulates have been admitted. The formula derived for the space part of the general rotation-free Lorentz transformation is very compact and allows for an easy derivation of the velocity and acceleration transformations. A possibly new and very simple relation is found between proper acceleration and acceleration in an inertial frame.Update of physics/0606103 4 pages, 1 figure, a slightly modified version is to appear in the American Journal of PhysicsGeneral Physicstext