Pulleys and Mechanical Advantage

This set covers definitions, types, and mechanical calculations for single, movable, and compound pulley systems.

Pulley

A grooved wheel with either a rope or chain and a steel cable or belt which lies in the groove, used to lift heavy loads, transmit power, or change the direction of force.

Single fixed pulley

A pulley with one wheel attached to a support (such as a beam or frame) that changes the direction of force but provides no mechanical advantage.

Movable pulley

A pulley consisting of a rope attached to some surface that directly supports the load and reduces the effort required to lift it, providing a mechanical advantage.

Compound pulley (block and tackle)

A system of ropes and pulleys where the total lifting effort decreases as the pulley system becomes more complex.

Mechanical advantage (MA)

A direct relationship between the number of ropes that form the pulley and the resulting benefit in lifting a heavy load.

Double pulley system mechanical advantage

A system where the mechanical advantage is equal to $2$, halving the amount of force while doubling the distance the rope must be pulled.

Newton ($N$)

The force exerted by gravity on a mass of $0,1\,\text{kg}$ (equivalent to $100\,\text{grams}$).

Mechanical advantage formula (Distance)

$$\text{mechanical advantage} = \frac{\text{distance moved by the load}}{\text{distance moved by the effort}}$$

Effort calculation (Compound pulley)

The effort needed to lift a load is determined by taking the weight of the object divided by the number of falls.

Rope pull distance (Compound pulley)

The distance the rope must be pulled, which is calculated as the distance the object is lifted multiplied by the number of force.

Workload reduction (Fixed and Movable system)

A combined system that reduces the workload by a factor of $2$ because the two pulleys combine to lift the load.