How do Pulleys Work?
- Oct 03, 2016
- Sudipto Das
A pulley’s a simple collection of one or more than one wheels through which a rope is looped in to make it easier for people to lift things.
Pulleys are examples of simple machines meaning they are generally devoid of engines and gears which are generally present in complex machines. Their main task is to multiply forces.
If anyone wants to lift a heavy weight beyond his/her capability, s/he can resort to pulleys to do the job. One can be the world’s strongest man/woman, but there must be a limit to his/her capabilities. But the use of pulleys (a simple machine) can effectively solve the problem to a certain extent by multiplying the force produced by the body.
The use of a 2-wheel pulley
Working of pulleys
The more wheels it has and the more times the rope is looped around them, the more you can lift.
If you’ve one wheel and a rope, a pulley aids you to reverse the direction of the lifting force. In simpler words, we can say that you will have to put the rope down to raise the weight up. So if you have to lift up a weight of 100kg, you’ll have to implement a force of 100kgf, which is somewhat equal to 1000N.
Single wheel pulley
With the addition of more wheels, you can actually reduce the effort required to lift the same weight that you have lifted using the single wheel pulley up above. Say, for example; you have a two wheel pulley along with a rope looped around them. You can refer to the image below.
Two wheel pulley
The 100 kg mass (as mentioned above in the single wheel pulley reference) is effectively supported by two sections of the rope. In this case, you’ll be able to lift the weight up by applying half the force implemented in the case above. That means you’ll have to implement only 500N while using a two wheel pulley to lift the weight up.
A pulley is similar to that of a lever
A pulley has the capability of magnifying force in a similar way to that of a lever. Let’s explain this in more detail with an example (see-saw). The seesaw is a lever. If you want to lift up a person who is four times heavier than you, you’ll have to place yourself four times further away from the fulcrum (balancing point) of the see-saw.
The same thing applies to that of a pulley with a small exception. In the case of a pulley, you are actually pulling on a rope instead of moving the ends of a seesaw. If you want to lift something that’s 4 times heavier than you with the help of a pulley, you can lift it up by using the exact force required to do the same by simply pulling the rope 4 times further. Thus, you have decreased the effort required to perform the job.
So we hope that you have had a good read of the topic and have actually gained a good enough insight into the subject. We’ll sign off for now. Ciao!
Sudipto writes technical and educational content periodically for wizert.com and backs it up with extensive research and relevant examples. He's an avid reader and a tech enthusiast at the same time with a little bit of “Arsenal Football Club” thrown in as well. He's got a B.Tech in Electronics and Instrumentation.
Follow him on twitter @SudiptoDas1993
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