Introduction to Pulleys

Pulleys are simple machines used to lift loads with reduced force. Employing wheels and ropes, they alter the direction of the applied force, enabling heavy objects to be raised with less effort.

A single fixed pulley changes force direction without a mechanical advantage. It means you apply the same force to lift an object as its weight, but the pulley lets you pull down instead of lifting up.

Mechanical advantage (MA) is the factor by which a machine multiplies the input force. For pulleys, MA equals the number of supporting ropes. More ropes mean less force required to lift an object.

Movable pulleys attach directly to the load, cutting the necessary lifting force in half but requiring more rope to elevate the object the same distance as with a fixed pulley.

Combining fixed and movable pulleys creates a compound system, significantly increasing mechanical advantage. These systems can lift heavy objects with minimal force, used in cranes and elevators.

To calculate the force needed in a pulley system, divide the weight of the load by the mechanical advantage. For a system with MA of 4 lifting a 100 kg weight, only 25 kg of force is needed.

Pulleys aren't just historical artifacts; they're vital in modern machinery. From construction cranes to theater curtains and gym equipment, pulleys continue to be indispensable in everyday life.