Talk:Angular momentum

The reason the proof of angular momentum was originally attached to Torque as a subpage, was because I considered the proof trivial, and not interesting to the majority of users interested in the article. In fact, I thought it would scare aware the math-phobic general public. I wrote it shortly after I rewrote Torque. The previous version of that article contained the misconception that the derivative of angular momentum is equal to torque only in special cases. I wrote Torque/Angular momentum proof to justify my alteration, to explain to whoever wrote the article why I'm right, and of course to increase the amount of information in Wikipedia by a tiny, trivial amount. I disagree with its inclusion in Angular momentum because the inclusion of this trivial, apparently random factoid is inelegant, confusing, and makes the article overly mathematical. -- Tim Starling 01:52 Apr 28, 2003 (UTC)

Only, it's non-trivial. To make it trivial requires certain quite reasonable assumptions - but a rigorous demonstration is far more awkward than (say) energy conservation. Essentially, in general you are dealing with an infinite number of particles. Then you have to assume that some terms in an infinite sum go to zero, which isn't obvious. PML.

That depends on your definition of trivial, doesn't it? There's trivial as in the maths is easy, and there's trivial as in List of songs which have the word Song in title or lyrics. I think it's both -- it's trivial mathematically for someone competent in the field, and also trivial in the sense that most people reading angular momentum or torque don't care about how to prove this identity. But I'm getting off the point. Even if it were non-trivial mathematically, it still shouldn't be in the article, due to the confusion factor. Since confusion factor increases with non-triviality, your statement seems to support my main point. -- Tim Starling 03:02 Apr 28, 2003 (UTC)

I would say it supports the reverse: since there is something to be said, it is better to note it than to slide past it. Your remarks, while accurate as far as they go, don't lead to us leaving it out but to us making the editing draw attention to the fact that there is more for interested people to follow up - without distracting casual browsers. The principle of a good encyclopaedia. Now, how to achieve both? If in doubt, I'd rather leave it in. PML.

How do we achieve both? Simple, by leaving it how it was when I wrote it, i.e. on its own page. That's the whole point -- I'm responding to Looxix suggesting merging Proof of angular momentum (which started out as Torque/Angular momentum proof) with Angular momentum, an act which I disagree with. Sorry if I didn't make that clear. -- Tim Starling 05:44 Apr 28, 2003 (UTC)

No problem for me, it was only an suggestion/question. In fact, until we have the possibility to link within a specific part of a page, I often prefer to have well linked small pages than one BIG page having all the sub-subject linked to the main article. -- Looxix 20:47 Apr 28, 2003 (UTC)

Contents

1 Tesla coil 2 Definition 3 diagrams 4 Cutting editorial comment from the article page here for discussion

Tesla coil

I removed the following paragraph, which seems a bit dubious:

A good model of angular momentum is the inventor Nikola Tesla's Tesla coil, where due to angular momentum of the field, a energy force can be pulled off at 90 degrees to the spin of the field on the coil, called phase,see also polyphase coils.

This might be true, but it's not very clear. What is an 'energy force'? -- Heron 19:33, 4 Jul 2004 (UTC)

Definition

I'm not happy about the definition used at the beginning of this article. I think we ought to be able to improve on this. I'd like to suggest the following. Any comments / improvements, please? Ian Cairns 22:37, 2 Oct 2004 (UTC)

"Angular Momentum is the tendency of an object orbiting an origin to continue orbiting. This is the rotational analog(ue) of linear momentum, and reflects the moment of the linear momentum of the object orbiting the origin. A body rotating about an axis can be considered to be the sum of its individual particles. Likewise the body's angular momentum can be considered as the sum of the individual angular momenta of all the particles' The SI unit of angular momentum is the kilogram metre squared radian per sec (kg m² s^-1)."

seconded if no one speak against, i'll implement it next week. 12 Dec 2004

diagrams

Diagrams!!! We need diagrams! Otherwise it is very hard for young students to understand what is being talk about in this article. For example the angles. Without diagrams the young students are merely guessing where the angle is measured from.

Post requests to Wikipedia:Requested pictures, if you will. —Josh Lee 02:39, May 6, 2005 (UTC)

Cutting editorial comment from the article page here for discussion

I cut the editorial comment below for someone to integrate as text in the article page.

• • • • Comment from somebody else: this only defines "torque" as being the time derivative of angular momentum - when is the torque zero? Torque does not appear in any of Newton's laws, and should therefore not be used to explain under which circumstances angular momentum is conserved. The time derivative of the angular momentum is not a law in analogy to Newton's second law, but a consequence of Newton's law: simply take the time derivative of the angular momentum as defined above, and plug in Newton's laws. It then follows that a particle in a central force field has its angular momentum conserved. This was shown explicitly in a previous entry on angular momentum, which has been removed. *******

The above editorial comment was added in this edit (http://en.wikipedia.org/w/index.php?title=Angular_momentum&diff=0&oldid=9149664). ---Rednblu | Talk 20:58, 6 Jan 2005 (UTC)