To make a rope taut, it must be pulled outward by external forces F at both ends.
A taut rope in turn exerts inward tension forces T at both ends.
In A-level, the scenarios are usually idealised so that the tension forces at both ends of the rope can be assumed to be equal in magnitude.
a “light” rope in practice means that the rope must be pulled equally hard at both ends, since the tiniest imbalance between the forces would imply an infinite acceleration.
a “light” rope also means that a vertical taut rope does not have to support its own weight.
a “light frictionless” pulley in practice means that the frictional force the rope must exert on the pulley in order to rotate the pulley is negligibly small.
