How are pulleys used

Pulleys are one of the simple machine.It consist of a wheel with a groove along its edge,that holds a rope or cable.This makes pulleys useful for lifting of heavy objects.Example of pulleys-
1.Elevators used multiple pulleys in order to function.
2.Wells used pulley system to hoist the bucket out of well.
Usually two or more pulleys are used together,as it reduces the amount of force required to lift the load.Inspite of this, pulleys can be attached to cranes for lifting extrmely heavy objects.In spite of this it can also be realigned to change the direction of applied force.

A pulley is a wheel on an axle that is designed to support movement and change of direction of a cable or belt along its circumference. Pulleys are used in a variety of ways to lift loads, apply forces, and to transmit power. A pulley is also called a sheave or drum and may have a groove between two flanges around its circumference. The drive element of a pulley system can be a rope, cable, belt, or chain that runs over the pulley inside the groove.

A rope and pulley system -- that is, a block and tackle -- is characterised by the use of a single continuous rope to transmit a tension force around one or more pulleys to lift or move a load—the rope may be a light line or a strong cable. This system is included in the list of simple machines identified by Renaissance scientists.

If the rope and pulley system does not dissipate or store energy, then its mechanical advantage is the number of parts of the rope that act on the load. This can be shown as follows.

How it works:
The simplest theory of operation for a pulley system assumes that the pulleys and lines are weightless, and that there is no energy loss due to friction. It is also assumed that the lines do not stretch.

In equilibrium, the forces on the moving block must sum to zero. In addition the tension in the rope must be the same for each of its parts. This means that the two parts of the rope supporting the moving block must each support half the load.
Please refer to the diagrams attached hereunder.
simple pulleyMovable pulley