When there is no gain in mechanical advantage of a single fixed pulley, why is it then used?
Although there is no gain in mechanical advantage, but due to following reasons, we are using single fixed pulley:
To raise a load directly upward is difficult, so applying effort in the downward direction ( even we can use our own weight for the effort), we can move the load upwards conveniently.
Used to change the direction of force applied to a more convenient direction
