What Are The Uses Of Pulleys?

The original primary use for pulleys was to make it easier to lift heavy items. A pulley is a simple machine made with a wheel and a rope, cord, or chain.

Pulleys can be found everywhere to help make tasks easier. In addition to lifting things, pulleys can be used singly or with many pulleys working together to transport people or things. They can also be used to provide power from one shaft to another.

Examples Of Pulleys In Everyday Life

Examples of pulleys include:

Elevators: Elevators      work via a powerful electronic pulley system. In fact, elevators make use      of a system of several pulleys and counterweights to provide the lift      system with both power and safety.

Wells:      Old-fashioned “wishing well” style water wells use the simple pulley      system to hoist the bucket out of the well.

Exercise      equipment. Most weight-lifting exercise equipments uses      pulleys to control the angle at which weights are lifted while keeping the      weights themselves in a dedicated location. This makes the process of      weight lifting safer and more effective for the user than free weights      maybe if used improperly.

• Construction      Pulleys. Construction pulleys are some of      the most basic and common pulleys, good for viewing the basic functioning      of this simple machine. These pulleys consist of a wheel track that can be      raised to great heights, fitted with chains or rope attached to hooks.

• Theater      Systems. In theaters, curtains and fly systems operate      using a system of multiple pulleys. These pulleys are located high above      the stage where the audience cannot see them and operated from the side of      the stage to raise and lower curtains and pieces of scenery during a      theatrical performance.

• Cargo      lift system. A cargo lift system that      allows for items to be hoisted to higher floors is a pulley system.

• Blinds      on windows. Blinds on windows operate using a pulley      system to move the blinds up and down. You pull the cord on the blinds and      the pulley system causes the blinds to open or close.

  Flagpoles. Flagpoles      use pulleys to hoist the flag up or to bring it down. You pull the s

  tring      on the pulley and the flag runs up or down the pole.

  Crane,      Bulldozer, Escalators utilize pulley systems to      function.

  Garage      doors, Sailboats, Engine, extend ladders, Rock climbers,      all Use pulley system to work safer and more effectively.

These are all examples of pulleys. A cable system makes it easier to lift or move objects. Pulleys are required to move and lift very heavy or large objects. The simple principle behind pulleys makes them one of the most effective tools out there.

How pulleys work

The more wheels you have, and the more times you loop the rope around them, the more you can lift.

One wheel

If you have a single wheel and a rope, a pulley helps you reverse the direction of your lifting force. So, as in the picture below, you pull the rope down to lift the weight up. If you want to lift something that weighs 100kg, you have to pull down with a force equivalent to 100kg, which is 1000N (newtons). If you want to raise the weight 1m into the air, you have to pull the loose end of the rope a total distance of 1m at the other end.

Two wheels

Now if you add more wheels, and loop the rope around them, you can reduce the effort you need to lift the weight. Suppose you have two wheels and a rope looped around them, as in the figure below. The 100kg mass (1000 newton weight) is now effectively supported by two sections of the same rope (the two strands on the left) instead of just one (ignoring the loose end of the rope you're pulling with), and this means you can lift it by pulling with a force of just 500 newtons—half as much! That's why we say a pulley with two wheels, and the rope wrapped around it this way, gives a mechanical advantage (ME) of two.

Mechanical advantage is a measurement of how much a simple machine multiples a force. The bigger the mechanical advantage, the less force you need, but the greater the distance you have to use that force. The weight rises 1m, but now we have to pull the loose end of the rope twice as far (2m). How come? To make the weight rise 1m, you have to make the two sections of rope supporting it rise by 1m each. To do that, you have to pull the loose end of the rope 2m. Notice that we can also figure out the mechanical advantage by dividing the distance we have to pull the rope by the distance the weight moves.

Four wheels

Okay, what if you use four wheels held together by a long rope that loops over them, as in the picture below? You can see that the 100kg mass (1000 newton weight) is now hanging from four sections of rope (the ones on the left, ignoring the loose end of the rope you're pulling with). That means each section of rope is supporting a quarter of the total 1000 newton weight, or 250 newtons, and to raise the weight into the air, you have to pull with only a quarter of the force—also 250 newtons. To make the weight rise 1m, you have to shorten each section of the rope by 1m, so you have to pull the loose end of the rope by 4m. We say a pulley with four wheels and the rope wrapped around like this gives a mechanical advantage of four, which is twice as good as a pulley with two ropes and wheels.

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