Talk:Lagrangian mechanics

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Examples of Use (Applications to CS and Engineering)[edit]

Would it be wise to include examples where Lagrangian Mechanics are useful compared to Newtonian Mechanics? CessnaMan1989 (talk) 03:23, 30 September 2020 (UTC)[reply]

Sure! We can discuss them here first, if you want. Which ones did you have in mind? Ponor (talk) 04:40, 30 September 2020 (UTC)[reply]

Ok, I'm sorry I had already put two in. I was thinking of mentioning how Lagrangian Mechanics are convenient for tracking drones, and I linked to a paper about it. I was also thinking of posting articles about how it has inspired many Deep Learning and AI algorithms too.CessnaMan1989 (talk) 20:45, 1 October 2020 (UTC)[reply]

@CessnaMan1989: with all due respect, I don't think your addition belongs to this article. Shouldn't this rather be an example of optimization problems or calculus of variations? The whole new section reads like an advertisement, and to an uninitiated doesn't really mean much. In the paper you cited (are you one of the authors? careful with that, wiki prefers secondary sources, not original research!), what would even be the F=ma equation, what's the recipe (I am asking because you're saying Lagrange is easier than Newton)? What are T and -V in the Lagrangian? How does one generalize to other similar optimization problems? Ponor (talk) 23:55, 1 October 2020 (UTC)[reply]

I agree with Ponor. Also, claims like the one CessnaMan1989 is making need to be backed up by several mutually independent sources. Otherwise, this is a WP:POV issue. StrokeOfMidnight (talk) 04:40, 2 October 2020 (UTC)[reply]

Okay, :@Ponor: and :@StrokeOfMidnight: I will revert the edit and draft before posting again. I'm definitely NOT one of the authors of this paper, but I was just offering it as an example. I can find lots of original research to cite, but only a few secondary sources on the matter simply because this is a very niche area of academia. Most people who learn about Lagrangian mechanics, especially the engineers, only do so in graduate school now. As a result, there just aren't as many textbooks on the subject. Still, there are textbooks such as "Theory and Applications of Multitethers in Space" by Panfeng Huang and Fan Zheng that demonstrate the benefits of Lagrangian Mechanics in simulations. — Preceding unsigned comment added by CessnaMan1989 (talk • contribs) 15:45, 4 October 2020 (UTC)[reply]

Curly L?[edit]

Would it not be more standard / look better to uses a curly ${\mathcal {L}}$ for the Lagrangian rather than a regular capital L?

Blitzer99 (talk) 22:21, 2 December 2020 (UTC)[reply]

@Blitzer99: I agree. This is a convention I've usually seen followed, especially because in a lot of places people use L for angular momentum as well, which may lead to confusion. It ought to be changed. EffyJohn (talk) 15:43, 30 September 2021 (UTC)[reply]

Possible error in the introduction using the terms ″variation″[edit]

In the introduction of this page the term $\delta {\mathcal {S}}:[t_{0},t_{1}]\rightarrow \mathbb {R}$ is defined and called the ″variation″, which is possibly erroneous (although $\delta {\mathcal {S}}$ is indeed a Gateaux derivative). Comparing $\delta {\mathcal {S}}$ with the definition of ″variation″ (of $x_{0}$ ) in the Wikipedia page virtual displacement, one finds instead that a variation is a function as well of the parameter ε. In other words, the "variation" is not equal to the "Gateaux derivative". However, it might be that the term "variation" is defined in some other way (which is then inconsistent with the definition in virtual displacement). Doubledipp (talk) 16:45, 16 April 2022 (UTC)Doubledipp[reply]

There is some discrepancy between math and physics in how the term "variation" is used. In math,

\delta {\cal {S}}

could have been (and is in some sources) called infinitesimal variation. StrokeOfMidnight (talk) 06:46, 20 April 2022 (UTC)[reply]

Lead section rewritten[edit]

I've rewritten the lead section per MOS:INTRO to get rid of the equations and the more complicated mathematical language. All of that stuff appears later in the article, and the lead needs to provide a less technical overview of the topic.PianoDan (talk) 20:05, 25 April 2022 (UTC)[reply]