Fig 7Pulleys trade distance for forceideal, frictionlessMA = strands holding the load
Tension is the same all along a rope that runs over frictionless pulleys. So the load is held up by however many rope strands support its pulley, each pulling with the force you apply, and you only need W ÷ (number of strands). A fixed pulley just changes direction. One movable pulley halves the force. A four-strand block and tackle quarters it. Nothing is free, though: to lift the load 1 m with four strands, you pull 4 m of rope. Work in = force × distance = work out.