How Pulleys Work

A example of a simple pulley system and how it works.

Category:

Education

Tags:

• Science
• Physics
• Simple
• Machines

[paramo81]

i had a question, so if you take the extra dumbell you had at the beggining of the video, and attatched it to the pull end of the rope 2 feet up, will the 1 lb of wieght actually lift the load of the 1 lb dumbell, seeing as how it only takes a 1/2 pound to lift it? this might be a good visual point to make in the future?

[charliemarz]

@paramo81 Yes a one pound weight would lift the one pound load. In fact any weight slightly larger than one half pound would lift the one pound load.

[Vamperlis]

and 2. People say that the fixed pulley up top is ONLY to allow you to pull down rather than pull up. But it seems to me, that if that fixed pulley were attached by a thread----a very very very tiny thread, strong enough to hold only the weight of the pulley---then when you put the rope over that pulley and pull down, I imagine that the thread holding the pulley would break. That would reason that the fixed pulley is supporting the load at least a little. Am I wrong??

[charliemarz]

@Vamperlis

I believe that the fixed pulley does exert a force on whatever is supporting it.

However, no motion and therefore no work is associated with this pulley.

[Vamperlis]

Thank you for the video, but I have 2 questions for you:

1. The impression I get is that the reason you can use less force when you use a moveable pulley is because half of the weight is supported by the fixed end of the string. BUT, imagine that you turn a pulley horizontally. For instance, maybe one end of a rope is attached to a wall, and there is a giant boulder that the rope goes behind and you have the other end of the rope. Why would it give you a mechanical advantage here?

[charliemarz]

@Vamperlis

In this case, the force we are working against is friction. No force is is

exerted on either side of the rope until you start pulling. Once you start

pulling there will be tension on the side of rope you are holding as well the

rope attached to the wall. The force on the boulder is the sum of these two

tensions. If you pull the rope a distance of two feet, the boulder will only

move one foot.

[Zergling924]

thank you so much for this video - it has helped me immensely in teaching a student of mine! (i don't happen to have a pulley system on hand for demonstrations, haha)

[MrMoneymeister]

Yay!

[runr100]

Nicely done...perhaps you could add more pulleys?

[whitebelt23]

thank you very much!



[zealandzen]

Great video. Succinct. Good visuals. Repetition of facts is key. Much appreicated. Let's see more science videos like this one.

[byproxy97]

@Vamperlis i agree with you. the fixed pulley would support a little of the weight, but I think mainly it is to redirect the pulling. Which is exactly the use of a single fixed pulley, redirecting force. But ya, either way I think it supports a fraction of the weight, but it would only matter on a larger scale.

[oppression99]

excellent video.