What Does a Pulley Do?

A pulley is basically an assortment of wheels that you can connect a rope, making it easy to lift things.

Pulleys are an example of what scientists refer to as simple machines. This doesn't mean that they're filled with motors and gears, it's just that they can help us to multiply forces.

If you're looking to lift a massive weight you can only use the power your muscles can produce even if you're the strongest person in the world. Make use of a device like an incline pulley to effectively boost the strength your body creates.

How do pulleys work?

The greater the number of wheels you have plus the greater number of times you wrap your rope, the greater you'll be able to lift.

One wheel

If you only have one rope and wheel, a pulley will help you reverse the force you are lifting. As in the image below you pull the rope down to raise the weight. If you wish to lift 100 kg of weight it is necessary to pull it down using the force equal to 100kg, which equals 1,000N (newtons).

If you wish to lift the weight one meter into the air, then you need take the rope's loose ends for a total distance of 1m from opposite ends.

Also Read: What's an Alternator in a Car

Two wheels

In the future, if you have more wheels, and wrap their ropes around, you'll be able to decrease the effort needed for lifting the load. Imagine there are two wheels and rope that is looped around them, like the image below. This 100kg weight (1000 Newton of weight) is now is supported by two lengths of that rope (the two strands to one side) instead of the one (ignoring the loose portion of the rope you're pulling) This means that you can raise the rope by pulling it with the force of only 500 newtons, which is half the force! That's why we refer to pulling a pulley that has two wheels and the rope woven around it in this manner provides an advantage in mechanical terms (ME) from two.

Mechanical advantage is the measurement of the extent to which a basic machine can multiply the force. The greater the advantage in mechanical terms is, the less force you require, but the longer you'll need to utilize the force. The weight is increased by 1m but we must extend the length twice to the same distance (2m).

What's the reason? In order to make the weight rise 1m, you need to create two rope sections supporting it rise by 1m in each. In order to achieve that you need to make the loose portion of rope for 2m. Also, we can calculate the benefit of mechanical through dividing how far required for pulling the rope by at which the weight is moved.

Four wheels

What is the result if you make use of four wheels that are joined by a rope that runs over them like in the image below? It's clear this 100kg weight (1000 Newton of weight) is hanging from four rope sections (the ones to the left, and not taking into account the loose end of the rope that you're pulling). This means that each section of rope holds one quarter of the total 1000 newton weight or 250 newtons. In order to lift the weight to the sky it is necessary to pull only half of the force.

That's also 250 newtons. In order to raise the weight 1m, you need to cut each piece of the rope by 1m. This means you need to pull the loose portion of the rope 4 meters. We call it a pulley with four wheels and a rope wrapped such a way gives an advantage in mechanical terms of four times more efficient than the pulley made of 2 ropes with wheels.