A pulley is a simple tool that can be used for many things, such as lifting heavy objects or to change the direction of applied forces for various means. A pulley is a very simple tool that consists of a wheel on a fixed axle that has grooves for keeping a rope or wire in place. This makes pulleys useful for lifting heavy objects using applied human force.
Pulleys can be used in many other instances. They can be attached to cranes, for instance, to lift extremely heavy objects that humans otherwise wouldn't be able to move. Pulleys can also be realigned to change the direction of the applied force.
When using a pulley, certain terms are commonly used. "Load," for example, is the word meant to signify the weight of an object being handled by the pulley. "Effort" is commonly used by engineers to refer to the amount of force that will be required to handle the load, or weight.
Pulleys can be used to lift very large loads when they increase in number, so the more pulleys that are employed, the greater the loads the system can handle. The only trade-off to this system is that as more pulleys are used, more rope is needed to feed the pulley system. This also leads to the force having to be applied for an increased amount of time.