Talk:Kinetic energy

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Further information: Self-powered dynamic systems

@JoeNMLC I have reverted a change to add template Further information: Self-powered dynamic systems to the section "Kinetic energy of systems". The section is about internal kinetic energy of eg the Solar System. The referenced article is about systems that use energy harvesting internally. While there might be some overlap, the referenced article is not "further information" about the concept of kinetic energy.

If the kinetic energy article had an Applications section, the reference article might be linked there. (this would have to be a general purpose section with more than just the single application). Johnjbarton (talk) 02:26, 8 July 2023 (UTC)[reply]

@Johnjbarton - Thankyou for explaining the revert. I'm totally okay with that. While I did have two semesters Physics, it was so many years ago, I am out of my element on this topic. Regards, JoeNMLC (talk) 03:12, 8 July 2023 (UTC)[reply]

Newtonian kinetic energy?

how Newton is related to history of kinetic energy?

It is classical kinetic energy and not whole classic Physics is produced by Newton. 79.202.40.58 (talk) 07:17, 27 August 2023 (UTC)[reply]

I agree. Fixed.

Resolved

Johnjbarton (talk) 14:53, 27 August 2023 (UTC)[reply]

Kinetic energy as a relative concept.

(Follow up from a previous topic)

One aspect of the current article concerns me: possession of kinetic energy. As I heard it put one time: energy is not a magical fluid added and removed from objects. Rather it is a relative property, useful only by comparison. Objects have different amounts of kinetic energy depending on the reference frame. We humans assign kinetic energy to objects based on our analysis of the object's velocity relative to our chosen reference frame.

In one sense this is obvious: velocity is relative. Object's don't possess velocity, thus they cannot possess kinetic energy. The difficult part is presenting this naturally and clearly for an introductory audience and with sufficient reliable references.

I think such changes are important for this kind of article as noted in WP:OVERSIMPLIFY.

My proposal is to first develop a short section explaining 1) why kinetic energy is not an object property and 2) why assigning kinetic energy to objects is so darn useful.

And second to make small changes to the article to reduce the dependence on the possession model. For example, rather than

the kinetic energy of an object is the form of energy that it possesses due to its motion

we might say

the kinetic energy of an object is the form of energy associated with its motion.

I will look for appropriate references first. Johnjbarton (talk) 01:04, 9 September 2023 (UTC)[reply]

Unfortunately I don't have the right books needed to add references to this article. Johnjbarton (talk) 22:39, 9 September 2023 (UTC)[reply]

Semi-protected edit request on 16 November 2024

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In the section on Relativistic kinetic energy, I would like to add this note citing Einstein himself for the Taylor expansion of the relativistic energy:

Although Einstein does not explicitly refer to a Taylor expansion, in equation 45 of The Meaning of Relativity, Einstein "develop[s] ${\displaystyle E}$ in powers of ${\displaystyle q^{2}}$ ". In equation 45, ${\displaystyle q}$ is the magnitude of the velocity ( ${\displaystyle q}$ is defined on page 38), and the velocity of light is the unit (page 46).

The note would be placed after the first mention of "Taylor expansion" in the article:

"This is done by binomial approximation or by taking the first two terms of the Taylor expansion<<insert note here>> for the reciprocal square root: ..."

-- 50.47.156.69 (talk) 22:24, 16 November 2024 (UTC)[reply]

Thank you for this source. I encourage you to register for an account and contribute directly. Johnjbarton (talk) 23:16, 16 November 2024 (UTC)[reply]

Thanks for adding the Einstein reference. I have converted it to a "Cite book" template, which adds a link to the exact page being referenced:

{{cite book |last1=Einstein |first1=Albert |title=The Meaning of Relativity: Four Lectures Delivered at Princeton University, May, 1921 |date=1922 |publisher=Methuen & Company Limited |pages=51-52 |url=https://en.wikisource.org/wiki/Page%3AThe_Meaning_of_Relativity_-_Albert_Einstein_(1922).djvu/63}}

That renders like this:

Einstein, Albert (1922). The Meaning of Relativity: Four Lectures Delivered at Princeton University, May, 1921. Methuen & Company Limited. pp. 51–52.

NB: My IP address changed.

--50.39.109.119 (talk) 01:20, 17 November 2024 (UTC)[reply]

Maybe we should link the free Google books version which has all the pages: https://www.google.com/books/edition/The_Meaning_of_Relativity/0nIxAQAAMAAJ?hl=en&gbpv=1&dq=approaches&pg=PA51&printsec=frontcover Johnjbarton (talk) 01:29, 17 November 2024 (UTC)[reply]

Thanks for updating the article with the cite book template. On the Wikisource page, there are navigation arrows at the top left corner. However, I agree that the Google books version would be a better one to link, because it is easier to navigate. Also, search terms are highlighted in yellow. Unfortunately, the page break means that readers will have to scroll down one page to see the highlighted text. --50.39.109.119 (talk) 02:09, 17 November 2024 (UTC)[reply]

Thanks for updating the link. It works fine. Interpreting what Einstein means by "q" took me some effort, which is why I added a second sentence to my original suggestion. Since E. is a primary source, it might be a good idea to add a secondary source making the same point about the classical kinetic energy being the limit at low speeds. --50.39.109.119 (talk) 02:40, 17 November 2024 (UTC)[reply]

Books that are cited over 5000 times are great sources. Nevertheless a newer source would be great. I'll note that a much bigger problem in this article is large chunks of text with no sources. Johnjbarton (talk) 02:55, 17 November 2024 (UTC)[reply]

Here is a newer source (Robert Resnick, Introduction To Special Relativity (Wiley, 1968)) for the relativistic kinetic energy as a series. WolframAlpha computes the Taylor series used in the expansion. --50.39.109.119 (talk) 04:14, 17 November 2024 (UTC)[reply]