Talk:Introduction to angular momentum

Units of measurement

It would be helpful if the table showing differences between linear momentum and angular momentum showed the differences in the units of measurement. This would reinforce the notion that it isn't reasonable to add linear momentum and angular momentum in the hope of arriving at some sort of total momentum. My understanding of the units, in the SI system, are as follows:

• linear momentum kg.m.s^-1
• angular momentum kg.m².s^-1

I'm not skilled at manipulating tables of this kind. If someone able to manipulate the table agrees with my request, feel free to go ahead and add another row! Dolphin51 (talk) 00:59, 2 March 2010 (UTC)

False statement

This is a false statement: "The direction of angular momentum is the same as the direction of the angular velocity." Yes there are special cases where this is true, but the article doesn't state this anywhere. —Preceding unsigned comment added by 160.39.54.149 (talk) 04:38, 8 September 2010 (UTC)

Relationship to kinetic energy content

If we regard the 2 basic entities of matter as being mass and kinetic energy of motion, we con make the following statement about angular motion: Angular motion occurs in such a manner that all the constituents of the moving system do not have the same quantity of kinetic energy of motion. Thus a system in angular motion cannot be said to have any uniform quantity of kinetic energy content of its constituents. And thus a discussion of the motion of such a system is reduced to that of its momentum (Mv) properties. When these are analyzed, it is determined that the kinetic energy contained in the individual matter components of the system vary directly in accordance with their distance from the axis of rotation of the system, so that the kinetic energy of each subcomponent is modified by the factor r, where r is the axial distance of the individual subcomponent to the axis. And when this modification of kinetic energy content is made for the matter of the entire system the system kinetic energy content number is changed from the kinetic energy content value (summation of MV^2 values) to the values (summation of MVr/2 values), and thus for a constant M and r value, the angular momentum value varies as the square root of the kinetic energy content value.WFPM (talk) 16:42, 15 March 2011 (UTC)

Good, add it. But in "the kinetic energy of each subcomponent is modified by the factor r, where r is the axial distance of the individual subcomponent to the axis", I think "radial distance" is clearer because it makes you think "length of the radius" instead "distance along the axis".

Even clearer would be replacing "axial distance of the individual subcomponent to the axis" with the shorter "distance of each subcomponent from the axis".

That's my 2¢ — and it's worth every single penny you paid for it! HelviticaBold 06:15, 10 February 2012 (UTC)

Misleading example

The leading paragraph contains the following sentence: A freely-rotating disk (like a Frisbee in flight or a tire rolling down a hill) has angular momentum. I believe this is misleading because it suggests that only rotating bodies possess angular momentum. The definition of angular momentum indicates that any object possessing linear momentum also possesses angular momentum, and the relationship between the linear and angular momenta is a function of choice of origin. Any vehicle of mass m moving at constant velocity v has constant linear momentum and constant angular momentum. If the choice of origin lies on the trajectory of this vehicle then the vehicle's angular momentum will be zero; but if the choice of origin is offset from the trajectory by a distance r then the vehicle's angular momentum will be of magnitude mvr and its direction will be given by the right-hand screw rule. Is there any objection to me incorporating this expanded view of angular momentum into the leading paragraph in place of the misleading example presently there? Dolphin (t) 22:36, 21 June 2012 (UTC)

It is a general good practice to make the first paragraphs of an article accessible to people with no prior knowledge of the subject. Further on in the article the description can go in depth.

Yes, the full scope of the developed concept of angular momentum is as you describe. But it's counterproductive to put that information in the opening paragraph.

Actually, a general problem of wikipedia content is eagerness of editors to be exhaustive. The result is an article that is technically correct, but only someone who is already an expert in the subject can understand it. When that happens wikipedia loses its educational value.

I think that is what happened to the Angular Momentum article, and for the sake of education editors felt a necessity for an article 'Introduction to Angular Momentum.' Changing the current leading paragraph into a hyper-correct version defeats the purpose of the Wikipedia entry 'Introduction to Angular Momentum.' Cleonis | Talk 06:34, 22 June 2012 (UTC)

Restore to mainspace

Wikipedia has a dozen articles in the “Introduction to” series. Each one provides an entry-level explanation of a topic that can be inaccessible to many readers. This is an application of Wikipedia’s policy to WP:Make technical articles understandable.

1. Introduction to eigenstates
2. Introduction to electromagnetism
3. Introduction to entropy
4. Introduction to evolution
5. Introduction to gauge theory
6. Introduction to general relativity
7. Introduction to M-theory
8. Introduction to the mathematics of general relativity
9. Introduction to quantum mechanics
10. Introduction to systolic geometry
11. Introduction to the heaviest elements
12. Introduction to viruses

Until 2015 there was an article titled “Introduction to angular momentum”. In 2015 it was rendered invisible by being redirected to Angular momentum. This was done without discussion among interested readers or the Physics project group.

I will cancel the redirect and return the article to the mainspace. If there is renewed interest in again hiding this article, that interest should be aired on this Talk page and also put before the Physics project group for their consideration. Dolphin (t) 13:00, 22 April 2022 (UTC)

I think it was better as a redirect. This article is not very good (as earlier discussion indicated), and I can tell from experience that there will be very little interest in fixing it. We shouldn't keep bad pages around just because they have "Introduction to" in the title. XOR'easter (talk) 14:02, 22 April 2022 (UTC)

Oppose the reinstatement of this poor article (agree with XOR'easter); all articles should be readable to all. Also, the merge proposal was up since 2013, so there was plenty of time (before 2015) for interested parties to comment. I've returned the redirect, and suggest a RfC in case you would like to bring it back. Klbrain (talk) 21:44, 22 April 2022 (UTC)

It is disappointing to see an unsupported reinstatement of this article again, inconsistent with the principles of WP:BRD. To clarify: a merge of Introduction to angular momentum to Angular momentum was proposed in 2013 and selectively implemented in 2015. As the edit there suggests, it was selectively implemented because the introduction to Angular momentum was already well-developed on this page, and hence a copy-paste edit would have been inappropriate duplication. There was a discussion of the merge on the Angular momentum talk page Talk:Angular momentum/Archive 2#Suggest merge, where Dolphin51 was involved in the discussion (opposing the merge at that time); so, it seems mistaken to suggest that the Physics project group were not consulted. Further, Articles to be Merged, are automatically listed at Wikipedia:WikiProject Physics (see the articles to be merged section there); angular momentum being part of the project would have meant that the merge proposal was listed there for 2 years. There was content saved from the introduction article and moved to the main page (with this April 2015 edit, for example). So, my position remains that effort should be put into improving angular momentum, rather than re-introducing the duplication on content; if a simpler introduction is needed, then the relevant project is Simple English Wikipedia. Klbrain (talk) 06:57, 23 April 2022 (UTC)

Yes, this diverts volunteers' time and energy, both of which are in short supply. In addition, it's not like WikiProject Physics is some official body which is required by wiki-law to sign off on all article merges and redirects. The idea that the merge proposal got insufficient attention just doesn't hold up. At the risk of belaboring the point, having an article around that is confusingly written and not actually a simpler explanation runs against the goal of making Wikipedia's technical articles understandable. It's a backward step. Furthermore, this edit rationale for undoing the redirect assumes that physicists cannot find a version one day old in a page history. XOR'easter (talk) 12:44, 23 April 2022 (UTC)