A rigorous definition of mass in special relativity, proposed in a recent paper, is recalled and employed to obtain simple and rigorous deductions of the expressions of momentum and kinetic energy for a relativistic particle. The whole logical framework appears as the natural extension of the classical one. Only the first, second and third laws of…

We show the impossibility of harvesting power from rotational motions by devices attached to the rotating object. The presentation is suitable for students who have studied Lagrangian mechanics. (Contains 2 figures.)