By the way if the pulley haven't friction how it's possible to transfer the force. I think of it like when a car want to roll on a street there must be a friction between tires and the ground for car to move otherwise the car is chocking in its place like when it's on an icy ground.
For a simple pulley it wouldn't matter if the wheel itself turns or the rope slides over it without friction. Does that help? But I think I need a bit more explanation. For sake of simplicity let us put it this way: Assume a plain shaft with no pulleys or wheels on it and just a rope hanging on it. There is a mass on one end of the rope and we are pulling the other end. Now by assuming there is no friction between shaft and the rope, how the force is actually being transferred between our hand and the mass?
I mean don't we need there to be a sequential exertion of contact forces to transfer the force exerted by our hand to the mass? Show 2 more comments. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name.
Email Required, but never shown. The Overflow Blog. Podcast Explaining the semiconductor shortage, and how it might end. Does ES6 make JavaScript frameworks obsolete? Featured on Meta. Now live: A fully responsive profile. Related 0. Pulleys have been used for centuries in the workplace to make lifting easier. Typically made with a rope and a wheel, a pulley allows a person to lift a heavy load without using as much force as would normally be needed. The term pulley is often used interchangeably with the word sheave, but this is not technically correct.
There are some differences between a pulley and a sheave. A pulley is one of six types of simple machines. The sheave is the rotating, grooved wheel inside the pulley. This is the piece that the rope fits into. A fixed pulley with no sheave changes the direction in which the force is applied to move the heavy load, but it does not change the amount of force needed.
Using multiple sheaves gives you a mechanical advantage. In fact, with each additional sheave you use in a pulley, you only need half of the original required force to move the object.
More sheaves will make the work easier, but it also adds friction. A fixed pulley is one in which the drum is secured to a single spot. While the force required to lift or move an object is no different than if you were lifting it by hand, the fixed pulley allows you to change the direction of the force needed. For example, when attached to a bucket pulling water from a well, a fixed pulled allows you to pull laterally to raise the bucket in a more convenient manner than if you were hauling a bucket of water up vertically, hand over hand.
The bucket of water will still feel like the same weight, but lifting is more convenient. A movable pulley is one in which drum moves as you are moving the load. There is no change in the direction of force that you need to apply, but the load will "feel" lighter than it is. If you were hauling a heavy hay bale up into the loft of a barn, for example, a movable pulley would make the load feel much lighter, although the direction you are pulling would be the same.
In a compound pulley system, there is both a moveable pulley as well as a fixed pulley. This means that not only does the load "feel" lighter, but you can also change the direction of the force. Although this type of configuration makes it possible to move heavy loads very easily, the tradeoff is that considerably more motion is required to do the work.
Pulleys can be multiplied in any number of ways to accomplish a variety of tasks.
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