A very useful form of machine for lifting is the pair of rope blocks (see right).
A simple example of this consists of a pulley, groved to accommodate the rope, top and bottom with a rope threaded round as shown.
Finding the velocity ratio (V.R.) of this 'simple machine' is best done by holding ropes (a) and (b) and lifting the bottom block bodily, say by 1 mtr.
When the load (w) had been lifted both ropes (a) and (b) will each have 1 mtr of slack in them so (p) needs to be pulled 2 mtrs to take up the slack.
Effort (p), therefore, moves 2 mtrs while the load (w) only 1.
The VR equals the distance moved by P divided by the distance moved by W = 2/1 = 2