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Four pulleys

[edit]
Original - This diagram of four pulley systems illustrates how increasing the number of pulleys increases the mechanical advantage (making the load easier to lift).
Reason
Today's Commons POTD, seems like a good candidate here as well.
Articles this image appears in
Mechanical advantage, this image would be a good addition to the pulley page were it not already crowded.
Creator
User:Prolineserver, User:Tomia. (minor edits by Stanisław Skowron)
All show that; 100 N... --Janke | Talk 20:40, 24 March 2008 (UTC)[reply]
Yeah... clearly I don't know my physics :) maybe that should be put in the caption... or, it's probably solved by anyone who reads the article. 128.175.80.58 (talk) 16:49, 25 March 2008 (UTC)[reply]
  • Oppose for now In addition to the control image of no force applied, it also seems odd that the height off the ground is constant; other changes are made to offset the addition of more pulleys to keep the load lifted 10cm. The image gives an immediate (and incorrect) impression that more pulleys do not lift the weight higher. Instead, we must look to the differing numbers to see that this is not the case. My recommendations: keep the lengths the same, adding pulleys each time and the depict weight rising successively higher off the ground.--HereToHelp (talk to me) 00:10, 25 March 2008 (UTC)[reply]
    • More pulleys would not lift the weight higher, more pulleys would lift the weight less with the same amount of rope displacement (denoted s on the drawing). On this drawing the displacement changes from figure to figure. Work done (work = force * distance) is the same in each case, the weight is always 100 N and always lifted 10 cm, and the product of the rope displacement and force is always the same (100 N * 10 cm, 50 N * 20 cm, etc.) -- atropos235 ✄ (blah blah, my past) 00:32, 25 March 2008 (UTC)[reply]
I suppose that's why we need images like this...(although there should be an image of the system at rest).--HereToHelp (talk to me) 00:51, 25 March 2008 (UTC)[reply]
As you said, Work=Force*Distance. I guess what I'm trying to say is rather than decreasing the force and increasing the length to keep the work the same, keep the length the same and let the force and work change in response to the addition of new pulleys. Does that make sense? It's been awhile since I've studied pulleys.--HereToHelp (talk to me) 23:32, 25 March 2008 (UTC)[reply]
That makes no sense. Period. The whole point of pulleys is to do the same job with less force. It's understood that that comes at the price of having to pull the rope farther. Just because you have this pet idea that it would be interesting to have an image that shows the rope being pulled the same distance doesn't mean it is useful to the actual topic at hand. Explain how it would better convey the purpose of a pulley by showing more pulleys lifting an object less high when the rope is pulled the same distance. — BRIAN0918 • 2008-03-26 17:39Z
Okay, sorry. I've already withdrawn my opposition, so back off, alright?.--HereToHelp (talk to me) 18:57, 26 March 2008 (UTC)[reply]
  • Suggestions. OK, here I go again (and I swore off commenting on diagrams). It seems pretty good as a diagram, but some possible improvements – at least some of these are pretty easy fixes, if someone can get in and edit it.
  1. Inconsistent alignment, e.g., all 's = ...' should be vertically aligned, all forces at the right of each figure should be aligned with each other, etc. Additionally the first ‘s=’ should be in the same relative position as the others, i.e., at the left of the hook, or the rest should be at the right.
  2. Symbols not defined (e.g., what’s FZ, FL, s, ...). They’re not given on the image description page, captions, or article. Is someone using this image just expected to know what they are? Doesn't that reduce its usefulness?
  3. Inconsistent scale - measure the lengths of the distances given; the scale changes, e.g., 40cm isn’t 4 x 10cm; the 10cm displacement at the hook on Fig1 is not the same as the 10cm at the load, etc.
  4. Displacements should probably more correctly be given in SI units (i.e., m, not cm), though I’m not overly fussed with that as long as it's consistent.
  5. On that matter, shouldn’t what the four images are showing be described, at least on the description page? There's sort of a description in the article, but it doesn't refer explicitly to this diagram. --jjron (talk) 03:05, 25 March 2008 (UTC)[reply]
  • The two that are dissimilar are the s on the left and the rope tension on the right, the one on the left is pushed to the other side to shorten the image, and the right most rope tension is so it fits in a "clear rope area" (?). The position of the rope displacement measurements change between them (drifting lower), but they are placed in the middle of the dimensioning line as is typical on engineering drawings.
  • I'm probably not the best person to judge this for ease of use/understanding, but because all the symbols are labeled with the amount with units it should be easily enough to infer. I agree that regardless, they should be explained on the description page though.
  • Accurate scale isn't always beneficial to figures, here I don't think it's that big of a deal as everything is dimensioned.
  • I prefer cm slightly because it's on a more human scale and doesn't require decimals
  • I'll go ahead and describe the image fully on the description page and more tightly integrate the article copy today or tomorrow. -- atropos235 ✄ (blah blah, my past) 00:54, 26 March 2008 (UTC)[reply]

Please fix the scale issues before I promote this. Thanks. MER-C 08:31, 31 March 2008 (UTC)[reply]

Scale adjusted. I uploaded the file over the original, not sure if I was supposed to do that or not; it seemed like a correction so it didn't warrant a new file. -- atropos235 ✄ (blah blah, my past) 17:48, 1 April 2008 (UTC)[reply]

Promoted Image:Four pulleys.svg MER-C 11:37, 3 April 2008 (UTC)[reply]

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