Resumen

In this paper we review the system made up by two blocks connected by a string over a smooth pulley with variable tension. One block lies on an horizontal surface and the another block is hanging vertically. We carry out a complete and systematic analysis for the tension of the string as function of the angle θ and the horizontal distance x, at static equilibrium. We find a symmetry-like that corresponds to two different configurations with the same tension and obtain the relationship that must satisfy two angles or two horizontal distances to obtain equal tension.