Talk:Friction

Article merged: See old talk-page here

Edit Request: µ of graphite

The referenced paper [44] Superlubricity of Graphite states µ below 0.001 instead of 0.01 139.30.239.150 (talk) 07:59, 25 April 2025 (UTC)

Declining the change. Martin Dienwiebel's paper does not define superlubricity, for which different people have slightly different values, so "below 0.01" is not incorrect. I added a ref to Martin Muser's paper which is in the Wikipedia link and the source of that number. In this article I don't think more is needed. Ldm1954 (talk) 08:29, 25 April 2025 (UTC)

Confusing edit

@Chjoaygame, unfortunately your recent change could be read to indicate that the force due to friction is a fundamental force. It is not, it is only the consequence of elastic/plastic deformation and others such as triboelectricity etc. Whatever goes into those is manifested as friction. Rather than my reverting your edit, can you please change it. Ldm1954 (talk) 11:11, 26 April 2025 (UTC)

@Ldm1954, thank you for your helpful comment, which I regard as valid. I will shortly try to do better, hopefully within a day.Chjoaygame (talk) 11:29, 26 April 2025 (UTC)

Looking again, I note that my initial edit https://en.wikipedia.org/w/index.php?title=Friction&diff=1287427495&oldid=1287295431 was only to the first paragraph; I left the other paragraphs untouched. I wonder if what you found unsatisfactory was actually in the second paragraph? I agree that the second paragraph has problems, but I planned to touch up the first paragraph before tackling the second paragraph. I have retouched the first paragraph. Enough for the moment. Your thoughts?Chjoaygame (talk) 11:55, 26 April 2025 (UTC)

Much of that first paragraph was a digression -- polishing etc has nothing to with the work done. I trimmed it.

I need to do some work on this article, parts are a bit of a mess. Toooo bust at the moment. Ldm1954 (talk) 12:18, 26 April 2025 (UTC)

Delete the "Energy due to friction section"

That section is a combination of somewhat vague statements plus some unsourced opinions about thermodynamic relevance that has no bearing on friction. I propose to take the first paragraph of the "Work" subsection, ensure that is goes somewhere earlier, and delete the rest. I will wait a few days for comments. Ldm1954 (talk) 12:31, 26 April 2025 (UTC)

There is no section titled “Energy due to friction” so I assume you mean the section titled “Energy of friction”. There is no subsection titled “Work” so I assume you mean the subsection titled “Work dissipated through friction”.

Are you proposing to retain the paragraph Friction is a response to a primary active force. Part or all of the energy transferred as work done by the primary force is dissipated as heat, deformation, wear, triboelectic charge transfer and changes of the contact surfaces. The dissipated energy does not enter the target body as work, and the dissipated energy per unit distance is what manifests as the frictional force., and delete the remainder of the subsection?

I agree that the remainder of the subsection is designed to confuse rather than enlighten. Much of it is unsourced. What value there is in the remainder can be salvaged and restored to the article, with sources, if someone is motivated to do so. I don’t object to your proposal. Dolphin (t) 13:38, 26 April 2025 (UTC)

"Failed to parse…" error

In the dry friction section

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "http://localhost:6011/en.wikipedia.org/v1/":): {\displaystyle F_\text{max}} Ludrol (talk) 09:57, 10 May 2025 (UTC)

I can't replicate that error again Ludrol (talk) 10:02, 10 May 2025 (UTC)

Change request: Dynamic friction coefficient of dry Aluminum on Aluminum

The provided value of µ=1,4 exceeds the range of the provided static friction coefficient of µє(1,05-1,3). This is physically impossible, since a dynamic friction coefficient being higher than the static coefficient would lead to a scenario, where an object on a slope of a specific angle would start to slide, since the projection of the gravitational force along the slope would exceed static friction. This would result in the dynamic friction coefficient being applied and resulting in a frictional force exceeding the projection of the gravitational force, immediately arresting the motion entirely. This essentially would make a differentiation between dynamic and static friction impossible in this scenario.

Viewed from another angle the implausibility of the coefficient of dynamic friction being higher than the static coefficient is highlighted further: The larger values of static friction coefficient can be traced back to atomic effects, such as interlocking of the crystalline structure, which are less prevalent in moving surfaces, resulting in lower dynamic coefficients. This should also apply to aluminum.

I discovered this discrepancy writing a lab report for my 3rd semester of physics and was confused as to why the here provided values were differing significantly from my own measured values of around 0,2054(21). Aluminum being a material with high sensitivity of the frictional coefficients to the condition of the used surfaces I expected a deviation of 100% to be somewhat realistic, but could not understand the significant difference of 700%. Other sources I subsequently sought out provided better fitting and physically possible coefficients of e.g.: µ=0,4 (source:https://www.engineeringtoolbox.com/friction-coefficients-d_778.html). This source also provided identical values to the ones sited here for the static friction coefficient of µє(1,05-1,3). Therefore I think a change of the value of the dynamic friction coefficient for dry aluminum on aluminum to µ=0,4 should be considered, since this at the very least provides a better approximation for general conditions and is not actively contradicting physical principles. P.GBL (talk) 20:50, 26 July 2025 (UTC)

Declined. If you can find (refereed) sources for a different values they can be added, but not otherwise.

What you are missing is that friction coefficients are not invariants for a given material, and can also depend upon the velocity -- this is very briefly mentioned in the article. An example is given for reduced friction with velocity. You will need to jump to a higher level of science than this page to understand this, for instance some of the papers on Google Scholar. Friction is much more complex than many people think, and there are still quite a few aspects which scientists do not fully agree on. Ldm1954 (talk) 21:38, 26 July 2025 (UTC)