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I genuinely don't understand how this works. It makes no

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Thread replies: 24
Thread images: 4

File: Polispasto2B[1].jpg (26KB, 375x659px) Image search: [iqdb] [SauceNao] [Google]
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I genuinely don't understand how this works. It makes no intuitive sense to me.

If I'd look at this I'd think you'd have to pull 100N since you not only have to lift the weight but also got friction on the rolling parts.
Someone explain this magic to me. I'm a fucking retard.
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>>7645552
more than 100N*
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>>7645552
Anything with numbers like this doesn't include friction. The weight is split in half. 50 going to the ceiling through the purple part of the pulley, and the other 50 going to the long part of the rope. All the pulley does is change the direction of the force. It changes the red 50 so that it pulls up on the weight
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the top pulley is weight bearing hth
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This just distributes the impulse over a greater period of time, right? Or am I completely off?
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>>7645567

dont use impulse
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draw a FBD you retards
and you guys wonder why people shit on the dumbshit ideas you post here, saying we're "closed-minded" or some shit
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>>7645573
I don't know what FBD is, sry. I don't usually frequent this board. I just thought maybe someone can explain this to me in simple terms.

It's such a great invention but I don't get it.
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Is this really saying 50N is enough to lift a 100N weight? That just doesn't make sense, isn't it just saying that 50+100 = 150 is the force the top pulley must be able to hold?
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>>7645574
the weight moves slower
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File: bt3[1].gif (9KB, 408x277px) Image search: [iqdb] [SauceNao] [Google]
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nvm I found a decent pic I think.

You only move it half the distance each pull since you're basically just lifting one side of the load-bearing rope, right?
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>>7645578
no. dont be a faggot
>>7645574
sum forces and set to zero. solve for tension in loose rope
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>>7645578
Yeah, thanks I got it now. This pic illustrates it a little better:
>>7645581

I'm a dumbass.
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File: sdasdsadsax.png (164KB, 653x659px) Image search: [iqdb] [SauceNao] [Google]
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>>7645552
>>
>>7645574
It distributes the "work" over a greater area; Think of a long lever with the fulcrum near the load you're lifting -- you have to move the end of the lever a long way in order to move the heavy load just a little bit. That's how a block & tackle works.
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>>7645582
found the redneck
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Why is mechanics so shit-tier in rigor?
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>>7645552

Kek, someone can't into relative motion
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>>7645581
eh
isn't that a shitty pic because with the ropes at an angle you are going to be losing force?
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The top pulley must support the weight as well as the downward tug on the rope, which totals to 150 Newtons. Since the leftward rope between the two pulleys is supporting half the weight of the metal weight, the other half is transferred over the top pully to the force tugging on the rope. However, the work-energy theorem states that you will have to pull twice the distance to achieve the same change in height.
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File: this.png (114KB, 469x537px) Image search: [iqdb] [SauceNao] [Google]
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>>7645585
this
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Think of it in terms of energy/work. W = Fd. Since there are two lengths of rope supporting the mass, you need to shorten each by the length d in order to raise the mass by that much. Combined, that makes 2d, which is how far you have to pull the rope.

F(pull) * 2d = F(mass) * d

Basically it's like a lever. You're pulling farther, so you don't have to pull as hard.
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>>7645826
No, it turns out that it doesn't matter. Gravity pulls down only, and pulleys make the horizontal forces balance out.
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>>7647540
Oh, but on second thought I see what you mean... shortening the rope supporting the weight by a particular distance doesn't raise the weight by that distance... so there's a trigonometric relationship there.
Thread posts: 24
Thread images: 4


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