Free Pulley

Free pulley can be moved freely at the time used, consider drawing the pulley on the side. In a state of balance on a pulley free to apply: W. Lb = F. lk

If you look at the picture, then at the free pulley, big arm power equal to twice the load arm. So that the mechanical advantage on free pulley size two (2) times, namely:
Km = W / F = 2 or Km = Lk / Lb = 2