What is a simple pulley?
A simple pulley is one of the six simple machines that are used in themselves or as part of more complex machines. Unlike complex pulleys, simple pulleys use only one rope, string or belt to reduce the amount of work needed to raise or move the object, regardless of the number of pulleys that are used together. These machines are very useful for lifting or moving heavy objects. The simple pulley was invented by Archimedes in the 3rd century BC (B.C.E.) and was adapted to many different uses, although in the last few millennia its design has changed very little.
Rope, bike and axel are part of a simple pulley. The wheel is attached to the axel, which is the center of the machine and which allows it to spin freely. The rope is then run around the wheel outside, so it touches approximately 50% of the wheel perimeter. Most pulleys have an edge with a lip or an outer cloak to prevent the rope from slipping.
One end of the rope is connected to an object that needs to be lifted, and the other end to a person, an animal or another machine that will apply the strength to the object by pulling it to the rope. All pulleys in the system are located above the object to be lifted, with the lowest pulley directly above the object and the highest pulley at the maximum height to which the object can be lifted. Extremely heavy objects can be easily lifted with enough deceptions and a sufficiently long rope.
In a simple pulley system, one pulley can be used separately or many can be used together. If there are more pulleys in the system, they are located vertically distant from the second and the rope is carried out alternately from the higher pulley to the lower. The only simple pulley reduces the amount of work needed to move the object by allowing a person to apply the strength in motion down while lifting the Object up. This event will cancel the gravitational force that affects the object, which makes it easier to lift. PUsing more than one pulley, it reduces the amount of force needed to lift the object by half every time the pulley is added, although twice as much rope is also required.