Talk:Work (physics)/Archives/2012/May

Confusing notation?

Is there any particular reason for using Newton's 'dot' notation in the proof in the Work and Kinetic Energy section? I suspect most readers will be more familiar with the notation used in one of the talk sections above. i.e:

$W=\int _{t_{1}}^{t_{2}}\mathbf {F} \cdot \mathbf {v} dt=\int _{t_{1}}^{t_{2}}F_{t}\,vdt=m\int _{t_{1}}^{t_{2}}v\,{dv \over dt}\,dt=m\int _{v_{1}}^{v_{2}}v\,dv={\tfrac {1}{2}}m(v_{2}^{2}-v_{1}^{2})$

1812ahill (talk) 22:41, 13 May 2012 (UTC)

Yes. On Wikipedia, the User who does the work gets to choose the notation. Whoever did the good work behind the Work (physics)#Work and kinetic energy section preferred the Newton dot notation. If you think the article can be improved by changing to a different notation, you may be right. In this case, it would be appropriate to alert other interested Users by making your argument here on the Talk page. If there is agreement, or if no-one comments, you are at liberty to go ahead and change the notation. Dolphin (t) 23:06, 13 May 2012 (UTC)

There may be a small confusion regarding "Newton's dot notation." Newton used a dot over a symbol to denote a time derivative. The "dot product" between two vectors was introduced as part of quaternion calculations and encoded in vector physics by Gibbs. These operations may seem formidable for Wikipedia but they are central to the derivation of the theorem relating Work and Kinetic energy. I understand why the symbol F_t is proposed, but in my opinion this simply hides well-known and important calculations behind unnecessary notation. More importantly the integration of velocity is limited to one dimension. The only way to make this calculation in two and three dimensions is using the vector notation provided. Prof McCarthy (talk) 03:46, 14 May 2012 (UTC)

By 'Newton's dot notation' I did mean the dot over a symbol notation. The example I copied above was simply because of the rusty state of my maths as I couldn't remember the phrase 'Leibnitz notation'! I appreciate the need for vector notation in the derivation, but this could surely be done just as easily using Leibnitz notation. It's just a suggestion, as during my academic days the only instance in which I can remember using dot notation was at (UK)A-level in the treatment of simple harmonic motion. We never used it in undergraduate Physics. I don't know about the case of engineering. Is it common to use this notation there?1812ahill (talk) 08:01, 14 May 2012 (UTC)

On second thoughts I am wrong. Leibnitz notation would make the whole derivation excessively verbose and longwinded. Perhaps, instead it might be useful to work the above equation into the section at the end as an example of the simplified one dimensional case to assist people unfamiliar with the dot notation?1812ahill (talk) 08:08, 14 May 2012 (UTC)

I think that would be helpful. Prof McCarthy (talk) 11:29, 14 May 2012 (UTC)

Added.1812ahill (talk) 23:13, 26 May 2012 (UTC)

Layman's terms

It seems that an editor feels the wording "product of a force times the distance through which it acts" is too technical. Therefore our colleague provides: "work is done when a force moves an object in the direction of the applied force." There are several things wrong with this statement, which were the reason for the general statement in the lead paragraph and the increasingly general examples in the following paragraphs.

It is important to realize that an object is not needed to measure work, simply the point of application of the force. Furthermore, it is not necessary that the point of application move in the direction of the force. In fact the point of application can follow any trajectory. In my opinion, this layman's explanation is not helpful. Prof McCarthy (talk) 04:48, 22 May 2012 (UTC)

I agree. The addition should be removed. This addition resulted from five edits made today by a new User. These are the only edits made by this new User. It would be appropriate to remove the new text and leave a message on the User's Talk page explaining the technical reasoning behind the removal, and explaining that Wikipedia requires encyclopedic language. Also, WP:NOT explains that Wikipedia is not a textbook. Dolphin (t) 05:51, 22 May 2012 (UTC)