# Talk:Net force

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WikiProject Physics (Rated Start-class, High-importance)

The third picture isk ya man, the resultant force should start at the intersection of the vectors A and B (near the letter 'e' in 'Object'). How would you add two unequal length parallel vectors (forces) at say the upper corners of the object, pointing at 1 oclock (30°)? —The preceding unsigned comment was added by 213.236.117.2 (talkcontribs) 09:58, 1 June 2004.

Vectors are not localized, it is assumed that the resultant force acts on the center of gravity of the object70.52.62.168 (talk) 01:04, 11 January 2008 (UTC)

## Net force versus resultant force

In many applications it is customary to distinguish the resultant force from the net force in case of extended bodies. I changed the lead to account for this, and also plan to re-write (accordingly) the rest of the article. Suggestions are welcome.--Ilevanat (talk) 20:47, 9 November 2011 (UTC)

I will need some time to finish the article. In its previous form it was so bad that it apparently invited series of vandalistic jokes, so I believe it is better to replace it with anything that looks more appropriate.--Ilevanat (talk) 01:42, 17 November 2011 (UTC)

I have completed the article in its new form. Please feel free to improve my English and style, and to add links to other articles (although I tried to include most relevant explanations in the text). Again, any suggestions are welcome.--Ilevanat (talk) 01:16, 23 November 2011 (UTC)

It would be helpful to add some existence theorems: under what circumstances is a resultant guaranteed to exist? Melchoir (talk) 03:02, 23 November 2011 (UTC)

Thank you for the edits, it looks smoother now. As for the existance issues, I am not aware of any general theorem. Have any proposals? (The graphical illustration actually demonstrates the two most common existance cases: concurrent and parallel forces - they obviously need not be planar.)--Ilevanat (talk) 01:27, 24 November 2011 (UTC)

## All edits after 14 December 2011 are either vandalism or ignorance

except for additions of links (and reverts). I am not very skilled in the article maintenance, so any help is welcome.

Of course, I shall gladly discuss any well intended changes on the discussion page (please, leave a note on my talk page).--Ilevanat (talk) 00:53, 30 January 2012 (UTC)

Understandably (I hope), my qualification "vandalism or ignorance" refers to the changes already made (before this note). And I would welcome any improvements in the future.

However, in order to clarify my views, additional explanation might be in order.

I re-wrote this article with intent to describe distinction between the net force and the resultant force, which is not universaly recognized in English usage, but it does appear in many English textbooks and, especially, in particular applications in mechanics. I believe the article is well ballanced and sufficiently referenced. But it is i bit technical, in order to make the point. The lead, I hope, is appropriately "lightweight".

One might object that some sections of this article should be better suited to the "Force" article, but that one has been generally recognized as an excellent article, and in its present form it is too non-technical for such content. (I did make some suggestions on its discussion page, but there was no response, so I gave up.)

This new version of the net force article has almost nothing in common with the previous one, which was fully unaware that there could be any distinctions between "net" and "resultant", and its graphical illustrations were almost childish. So I was rather surprised that an experienced editor undertook it to re-introduce such illustrations in the present version (somewhat modified, but still very far from the present level and context of the article, and far from correct from both formal and educational point of view). He shuffled them arround, and left some mess, but they obviously do not fit anywhere, unless the entire concept of the article is changed (reverted to the old version, or something like it).

Of course, I cannot claim the sole right to edit the article. And I am not going to start some lenghty dispute solving procedure, espicially since that editor does not see the need for any discussion. But I am enclosing here a brief dispute we had on his talk page (admitting that I was not too polite, but considering his education and editing experience, I could not take his intervention as a "good faith" deed):

#### I fail to see the purpose (or any benefit) of your edits in the "Net force" article

Nor did you offer any explanation at the discussion page. The drawings you inserted are nicely colored, but their content is fully covered by a prevous illustration, for which you inserted an entirely meaningless caption "Another method for diagramming addition of forces". That illustration shows all there is to show about addition of 2 forces. Or tell us what is missing! (Did you at all read the adjoining text?)

The closing section on usage discusses actual differences in approach by various authors. It could be improved by an illustration of a force reduced to a particular point, plus the ensuing torque, but that might be a bit too technical. Your drawings are entirely out of place there. (I cannot help wandering whether you have any understanding of the subject.)--Ilevanat (talk) 00:30, 30 January 2012 (UTC)

First off, I was replacing slightly incorrect diagrams that used to be there with corrected ones, a task that I was politely asked to do. I did check to make sure I was adding or demonstrating content. I was. Also, I love and teach chemistry and physics, mainly to Ivy League students. I know what I'm talking about and how I'm talking about it. If there's anything incorrect about the diagrams it was merely an oversight, but they are meant to be simplistic, just like their predecessors. As for the captions, this is Wikipedia. If you find something wrong with them, edit them. Like I mentioned, I did it as a favor for someone else and expected that the individual would edit the captions. I apologize for any inherent problems. 01:54, 30 January 2012 (UTC)
Also, adding uncontroversial content to an article does not warrant writing an explanation on a discussion page. 02:01, 30 January 2012 (UTC)

I am tempted to appologize for a bit harsh tone of my note. It was a "first off", as I saw the inappropriate editting of the article (the diagrams are too "simplistic" for the context, to say the least). But then, your explanation is rather incosistent, if not misleading. In particular, the "slightly incorrect diagrams that used to be there" were not in this version of the article, and their "replacement" does border with a revert of the article concept (so, it would be decent to discuss it). And I find it difficult to believe that you carefully read and fully understood the text (particularly after detailed examination of your 20 minute 4 edits). And I am not easily impressed by the Ivy League reference.

But I am not going to police the article. If you "Ivy League people" think this is better suited to the level of the English Wikipedia, so be it! Though I did record my opinion at the discussion page.--Ilevanat (talk) 01:12, 31 January 2012 (UTC)

## Applied and constraint forces

I have revised the lead to include in the definition of net force the applied and constraint forces on a free-body. It seems clear from this definition that the net force does not account for the points of application of the system of forces, and therefore the net force does not guarantee the same effect on a body as the resultant force and torque. I have tried to make this clear in the lead. Prof McCarthy (talk) 16:28, 1 August 2012 (UTC)

## Torque-free resultant

This article seems to define the resultant force as the special case when a system of forces can be reduced to a force at a particular point such that there is no associated torque. This seems contrary to the general notion of a resultant which consists of both a force and torque and is always available as a reduction of a system of forces and torques acting on a rigid body. I have introduced the term torque-free resultant, which I believe captures the original idea in order to minimize the revisions to the article. Prof McCarthy (talk) 01:06, 21 August 2012 (UTC)

## "Sophisticated" vandalism and lack of conceptual understanding

The article has seriously deteriorated through contributions by the author of the above two sections in this talk page. He generally has two fixations: to introduce constraint forces at any level of exposition (and certainly far sooner than it could possibly be appropriate, if ever), and to crowd the article with mathematical calculations (which are mainly correct, but rather disfunctional as many of them hardly help the reader to understand the subject). For this latter, the parallelogram rule is clear example in this article (and more can be seen in his edits of the Work article).

On the conceptual level, he tends to ignore prevalent usage (by professionals and in widely used textbooks) and his statements reveal some lack of basic physical understanding. For instance, he did not quite invent the definition "Resultant force refers to the reduction of a system of forces acting on a body to a single force and an associated torque" (implied in this article and written in his "new" Resultant force article), but in its support he cites a book from 1913 listed on the "Forgotten books" website. And then he states "However, an interesting special case is a torque-free resultant which it is useful both conceptually and practically, because the body moves without rotating as if it was a particle." He does not understand that the resultant force alone affects both translation and rotation, although that is explained even in his obsolete source.

Therefore, I can only again suggest my old version [1] of this article to any interested reader--Ilevanat (talk) 00:42, 4 September 2012 (UTC).