Talk:Friction

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A fact from Friction appeared on Wikipedia's Main Page in the Did you know column on 28 February 2004. The text of the entry was as follows: Did you know... that the Friction coefficient is very important in determining the friction between two objects? A record of the entry may be seen at Wikipedia:Did you know archive/2004/February.

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Article merged: See old talk-page here

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)Reply

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

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)Reply

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)Reply

"Friction between two objects. The blue one has more friction against the sloped surface than the green one." The blue object and the green object don't touch, so there's no friction between them! Maybe "Two blocks sliding down a slope."? ~2026-12129-51 (talk) 23:33, 23 February 2026 (UTC)Reply

Good catch. I changed it to "The blue plate has more friction on the sloped surface than the green one, so slides down slower." which seems better albeit a little clumsy. Ldm1954 (talk) 00:53, 24 February 2026 (UTC)Reply

I suggest changing the lead to refer to friction as a process rather than as a force, because many reliable sources describe friction more broadly as a process (or class of processes) that produces resistive forces, dissipates mechanical energy, and generates heat. Here is my suggestion:

change

Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding or grinding against each other.

to

Friction is the process of resistance to relative motion of solid surfaces, fluid layers, and material elements, sliding or grinding against each other.Chjoaygame (talk) 05:48, 23 March 2026 (UTC)Reply

I kindoff agree. For certain it is a range of dissipative processes. However "the process of resistance" is a bit too convoluted. Ldm1954 (talk) 12:28, 23 March 2026 (UTC)Reply

Thank you. What about

Friction is resistance to relative motion of solid surfaces, fluid layers, and material elements, sliding or grinding against each other.Chjoaygame (talk) 09:08, 24 March 2026 (UTC)Reply

I like that, go for it. Ldm1954 (talk) 11:28, 24 March 2026 (UTC)Reply

I removed content based on two sources.

1. Balitskii, O. I.; Kolesnikov, V. O.; Ivaskevych, L. M.; Havrylyuk, M. R. (2023). "The influence of specific features of load and hydrogen charging on steel tribotechnical properties". Materials Science. 58: 502–512. doi:10.1007/s11003-023-00691-5. Primary source with 11 citations. The claim added was obscure "Loading conditions combined with hydrogen charging may significantly modify tribotechnical properties of steels by influencing crack initiation behaviour and friction stability"
2. Balitskii, A. I.; Kolesnikov, V. O.; Balitska, V. O.; Ivaskevych, L. M. (2024). "Computer-Integrated Surface Image Processing of Hydrogen-Saturated Steel Wear Products". Applied Sciences. 14: 11762. doi:10.3390/app142411762.{{cite journal}}: CS1 maint: article number as page number (link) CS1 maint: unflagged free DOI (link) Primary paper with 8 citations. The claim added was not even about "friction", but about a measurement technique: "Advanced approaches to the analysis of wear processes in tribosystems include computer-integrated surface image processing techniques enabling quantitative characterisation of wear products and friction-induced surface damage."

In my opinion these minor topics should be sourced to secondary sources to ensure they are significant. However my removal was reverted by @Ldm1954 with a summary "Hydrogen embrittlement is definitely not a minor topic!", which is true but unrelated to my deletion. Johnjbarton (talk) 19:22, 24 March 2026 (UTC)Reply

This page suffered from major additions by various authors, IMHO without attention to the overall topic of the page. I have gone through and reorganized. At the moment there is nothing on the role of wear in friction, and it probably should be added with those (and other) sources used.

Vast amounts need work, some examples being:

1. A proper section on the nanoscale origins.
2. A proper sources section. Except for the 1st paragraph the material is just collated stuff from prior sections without any coherence.
3. Wear section as mentioned above.

Move "Types" below History or move History to the end? Ldm1954 (talk) 19:38, 24 March 2026 (UTC)Reply

I am unsure how reverting my delete is related to this reply. Johnjbarton (talk) 20:00, 24 March 2026 (UTC)Reply

I reverted your deleted, moved the statements, took them out for the moment and may reinstate. The section they were in is no longer present. As stated above, a section on the role of wear processes in energy dissipation should be included, and they might fit in there.

My apologies for skipping the details of why they are relevant, this is standard tribology. Ldm1954 (talk) 20:10, 24 March 2026 (UTC)Reply

Standard tribology would be supported by secondary references. Johnjbarton (talk) 20:12, 24 March 2026 (UTC)Reply