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Starting Anew- April 30th, 2008

My Edits

In this section, I'll be keeping track of all major physics related edits I've made and will also try to outline the reasons why did the edit.

In Uniform Circular Motion

Original:

The above picture shows a point of mass that is moving with a constant angular speed around a center. When the change in angle is ${\displaystyle \Delta \theta }$ , the change in displacement is ${\displaystyle \Delta }$s. Using the relationship of trigonometric functions, we find that,
${\displaystyle \Delta s={\frac {r\sin \Delta \theta }{\cos(\Delta \theta /2)}}}$

This equation is only valid when ${\displaystyle \Delta \theta }$ does not equal ${\displaystyle (2n+1)\pi }$ where n is integer.
Similarly, the magnitude of tangential speed is always the same. Let ${\displaystyle \Delta v}$ be the change in velocity, v be the initial velocity or instantaneous velocity, and ${\displaystyle \Delta t}$ be the change in time,
${\displaystyle \Delta v={\frac {v\sin \Delta \theta }{\cos(\Delta \theta /2)}}}$
${\displaystyle {\frac {\Delta s}{\Delta t}}={\frac {r\sin \Delta \theta }{\Delta t\cos(\Delta \theta /2)}}}$

When ${\displaystyle \Delta t\to 0}$, ${\displaystyle \Delta \theta \to 0}$,

${\displaystyle \lim _{{\Delta t}\to 0}{\frac {\Delta s}{\Delta t}}=\lim _{\Delta t\to 0}{\frac {r\sin \Delta \theta }{\Delta t\cos(\Delta \theta /2)}}}$

${\displaystyle v=\lim _{\Delta t\to 0}{\frac {r\Delta \theta }{\Delta t}}}$
${\displaystyle v=r{\frac {d\theta }{dt}}=r\omega }$ (${\displaystyle \omega }$ is angular speed)
${\displaystyle {\frac {r}{\Delta s}}={\frac {\cos(\Delta \theta /2)}{\sin \Delta \theta }}={\frac {v}{\Delta v}}}$
${\displaystyle \Delta v={\frac {v\Delta s}{r}}}$
${\displaystyle {\frac {\Delta v}{\Delta t}}={\frac {v\Delta s}{r\Delta t}}}$
${\displaystyle \lim _{\Delta t\to 0}{\frac {\Delta v}{\Delta t}}=\lim _{\Delta t\to 0}{\frac {v\Delta s}{r\Delta t}}}$
${\displaystyle a={\frac {v^{2}}{r}}}$

Because ${\displaystyle v=r\omega \!}$
We can substitute into ${\displaystyle a={\frac {v^{2}}{r}}}$
to get: ${\displaystyle a={\frac {(r\omega )^{2}}{r}}=r\omega ^{2}}$

Changed:

Magnitude

Assume ${\displaystyle \omega \!}$ is the angle in radians the body covers in unit time - in other words, the angular velocity of the body. Note that the rotational motion being uniform here we may choose any arbitrary unit for time with no change to the value of ${\displaystyle \omega \!}$ - so, without loss of generality, we assume that our unit of time is infinitesimally small.

The velocity vector, being always tangential to the circle, also turns by an angle ${\displaystyle \omega \!}$ in unit time.

The magnitude of instantaneous acceleration, by definition ,is the magnitude of vector change in velocity in an infinitesimally small period of time. The vector representing this is represented in blue in the above diagram. Since our unit of time is infinitesimally small, for all finite velocities, so will be ${\displaystyle \omega \!}$. Hence, the magnitude of the acceleration vector is ${\displaystyle v\omega \!}$.

Thus, we can conclude that the instantaneous acceleration experienced by a body in uniform circular motion is ${\displaystyle v\omega \!}$.

We may substitute ${\displaystyle v=r\omega \!}$ in ${\displaystyle a=v\omega \!}$ to get:
${\displaystyle a={\frac {v^{2}}{r}}}$

Direction

Since the magnitude of velocity never changes, the direction of the acceleration vector can only be perpendicular to the velocity vector. It can be seen from the diagram that this acceleration vector must point to the center of the circle.

Reason for Edit:

The original derivation was unnecessarily complex and leaves the reader with no feel for the underlying physics. I believe this derivation is direct and elegant - and the same time lets the reader see directly why the magnitude is v*v/r.

Image:Sunrise profile dilip.jpg missing description details

Move of Falun Gong and live organ harvesting

I have reverted your "move" because you did it the wrong way, per copy and paste. To move a page, you must use the "move" function at the top of the page, or else the history of the old page won't be carried over. See WP:MOVE. Also, before moving such a page, please make sure that you have consensus for it, and use correct capitalisation: "Reports of organ harvesting from live Falun Gong practitioners in China" instead of "Reports of Organ Harvesting from Live Falun Gong Practitioners in China". Sandstein (talk) 06:37, 4 May 2008 (UTC)

And please use edit summaries with your edits. Thanks, Sandstein (talk) 06:40, 4 May 2008 (UTC)

Orphaned non-free media (Image:Analysis Tianenmen False Fire GIF.gif)

Thanks for uploading Image:Analysis Tianenmen False Fire GIF.gif. The media description page currently specifies that it is non-free and may only be used on Misplaced Pages under a claim of fair use. However, it is currently orphaned, meaning that it is not used in any articles on Misplaced Pages. If the media was previously in an article, please go to the article and see why it was removed. You may add it back if you think that that will be useful. However, please note that media for which a replacement could be created are not acceptable for use on Misplaced Pages (see our policy for non-free media).

If you have uploaded other unlicensed media, please check whether they're used in any articles or not. You can find a list of 'image' pages you have edited by clicking on the "my contributions" link (it is located at the very top of any Misplaced Pages page when you are logged in), and then selecting "Image" from the dropdown box. Note that all non-free media not used in any articles will be deleted after seven days, as described on criteria for speedy deletion. Thank you. BJBot (talk) 12:16, 8 May 2008 (UTC)

Archiving

Hi there I've taken the liberty to be bold and archived your talk page from the history. It is bad practice to blank your talk page when you want to start anew, please see Help:Archiving a talk page for more details on how to archive the next time you want to start anew. --antilived 01:04, 11 May 2008 (UTC)

Thankyou :)

Dilip rajeev (talk) 05:07, 11 May 2008 (UTC)

Tiannamen Sq incident

Kindly do not revert when consensus is overwhelmingly against you, per WP:DE WP:EW and so forth. Blnguyen (bananabucket) 06:58, 13 May 2008 (UTC)

Hello back

You greeted me at my user page, and I want to say hello back. However, I am presently being considered for a one-year ban from wikipedia, and because this could happen any day, I want you to know that I received your greeting and greet you back. You may be interested in the discussion for the Arb committee on the subject of homeopathy that is presently taking place but may finish very shortly at: You may also want to see the Workshop page and the Proposed decision pages too, as well as the Discussion pages for each of these items. I do not mean to "canvass" you. I would send a similar message to anyone who contacted me directly through my user page and who does not seem to be aware of the Arb case at this moment. DanaUllman 00:36, 20 May 2008 (UTC)

CIPFG

If you get some free time, please have a look here, I would appreciate your comments on the CIPFG and Epoch Times, as they relay to the FG series of articles as a whole. MrPrada (talk) 18:15, 6 June 2008 (UTC)

rfc on bobby

I have notified Bobby fletcher that I will open an RfC on his conduct if he continues. I don't know if this is canvassing, as it's not my intention. Someone else needs to write on his talk page, asking him not to do any more incivility, personal attacks, assumptions of bad faith, etc.. You may wish to do so. diffs:

1. personal attacks, some assuming bad faith: , , ,
2. attempt at "outing", sometimes with personal attacks mixed in: , , -- Please note, these are only a sample. Attempted "outing" goes back months, and Fred Bauder oversighted it. But the user has continued recently.
3. original research: -- Please note, the user has not aggressively reinserted this after it was pointed out

--Asdfg12345 01:27, 26 June 2008 (UTC)