Talk:Slinky

Value of g

The acceleration due to gravity (g) is 32 feet per second per second NOT repeat NOT 16.

Possible copyright problem

This article has been revised as part of a large-scale clean-up project of multiple article copyright infringement. (See the investigation subpage) Earlier text must not be restored, unless it can be verified to be free of infringement. For legal reasons, Wikipedia cannot accept copyrighted text or images borrowed from other web sites or printed material; such additions must be deleted. Contributors may use sources as a source of information, but not as a source of sentences or phrases. Accordingly, the material may be rewritten, but only if it does not infringe on the copyright of the original or plagiarize from that source. Please see our guideline on non-free text for how to properly implement limited quotations of copyrighted text. Wikipedia takes copyright violations very seriously. — SamX [talk · contribs] 04:02, 28 August 2023 (UTC)

Possible physics mistake in derivation of the center of mass

In subsection https://en.wikipedia.org/wiki/Slinky#Equilibrium the last paragraph and the last equation shows that the center of mass of a slinky lies above a quarter of it's length from the bottom end. I believe this to be incorrect and I suggest that it is actually a third of it's length from the bottom end.

To support this I firstly would like to point out what I would consider to be a mistake in derivation of the proportion of 1/4 suggested by the article. The logic in the article is vague, but I believe that in order to get the center of mass the author found a position of a point which would divide a slinky into 2 parts of equal masses, and took that point as the center of mass. That is not how one should derive a center of mass. Consider the following thought experiment: suppose that the suspended slinky becomes rigid, and is placed on a pivot at that point. What you have is 2 levers of equal mass on both sides of the pivot, but that does not guarantee that the stiff slinky wouldn't rotate, as it wouldn't if it was placed on the center of mass. Similarly, if scales are balanced, that does not require for the masses to be equal. https://en.wikipedia.org/wiki/Lever#/media/File:Lever_Principle_3D.png

Since it is my first time posting anything on Wikipedia and since English is not my native language, I've decided not to edit the article, as I am not particularly familiar with the rules and I can't write well. Instead I propose for someone capable to double check where the center of mass is and to edit the article themselves how they would see fit, if they would find this issue significant.

During calculating the position of the center of mass, I derived an equation which might help to get the result:

⁠m²/h⁠=⁠M²/H⁠

Where:

M - total mass of the slinky,

H - total length of the suspended slinky,

h - length of the part of the slinky from the bottom,

m - mass of that part

That equation is equivalent to the second one from this subsection (https://wikimedia.org/api/rest_v1/media/math/render/svg/d7815aa5f70b25498e4774339832718b5247e557), but one might find it more convenient to use for the derivation. 178.64.226.149 (talk) 05:15, 28 February 2024 (UTC)

I assume now I should ping @Callitropsis:, since he is a recent contributor.

Also, I found this interesting diff: https://en.wikipedia.org/w/index.php?title=Slinky&diff=next&oldid=684188877 178.64.226.149 (talk) 05:39, 28 February 2024 (UTC)

Thanks for bringing this to people's attention. Most of my edits to the article were solely to resolve copyright issues (see the relevant CCI before it was blanked for background) and the most recent one was just a revert of some apparently well-intentioned but misguided copyedits. I have no experience with physics beyond a few undergraduate courses at university a few years ago, and I unfortunately don't feel qualified to comment on the physics aspect of this, which I have no opinion on.

I don't doubt that your calculations are correct, but they would constitute original research, which is not permitted in Wikipedia articles. We'd have to find a reliable source that supports your assertions to include them in the article. I know that rule probably seems unnecessary and bureaucratic, but it exists for a reason—if we didn't require reliable sources, we'd have no way to keep out the cranks who think global warming is a hoax because of the second law of thermodynamics, or that Earth is actually flat and NASA is part of some grand global conspiracy.

With that said, I certainly do appreciate that you've brought this up here. Original research isn't permitted in articles, but we absolutely can and should use critical thinking to evaluate the reliability of sources. If you can find a reliable source to support your claims (it doesn't have to be online or in English) feel free to post it here on the talk page or simply make the edit yourself. Your written English seems to be very good and Help:Introduction_to_editing_with_VisualEditor is a good primer if you're intimidated by the editing interface. I'd also recommend reading Wikipedia:Citing sources. Feel free to reply here if you'd like to discuss this further or reach out to me on my talk page if you have questions that aren't related to this. Thanks, — Callitropsis🌲[talk · contribs] 06:19, 28 February 2024 (UTC)

In the meantime, I've removed the section because it's not supported by sources. It's quite late in my time zone and I've been very busy recently so I probably won't be able to reply immediately to follow-up questions, but I will try to get back to you as soon as I can. — Callitropsis🌲[talk · contribs] 06:22, 28 February 2024 (UTC)