User talk:Dilip rajeev

Physics related Edits

“ You do not really understand something unless you can explain it to your grandmother. ” — Albert Einstein

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 for the edits.

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 $\Delta \theta$ , the change in displacement is $\Delta$s. Using the relationship of trigonometric functions, we find that,
$\Delta s={\frac {r\sin \Delta \theta }{\cos(\Delta \theta /2)}}$

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

When $\Delta t\to 0$, $\Delta \theta \to 0$,

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

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

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

Changed:

Magnitude

Assume $\omega \!$ 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 $\omega \!$ - 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 $\omega \!$ 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 $\omega \!$. Hence, the magnitude of the acceleration vector is $v\omega \!$.

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

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

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.

In Buoyancy

Original:

Pressure increases with depth below the surface of a liquid. Any object with a non-zero vertical depth will see different pressures on its top and bottom, with the pressure on the bottom being higher. This difference in pressure causes the upward buoyancy force.

The hydrostatic pressure at a depth h in a fluid is given by

$P=\rho hg\,$

where

$\rho \,$ is the density of the fluid,

$h\,$ is the depth (negative height), and

$g\,$ is the standard gravity ($\scriptstyle \approx \,$ -9.8 N/kg on Earth)

The force due to pressure is simply the pressure times the area. Using a cube as an example, the pressure on the top surface (for example) is thus

$F_{\mathrm {top} }=d^{2}\rho h_{\mathrm {top} }g\,$

where $d$ is the length of the cube's edges. The buoyant force is then the difference between the forces at the top and bottom

$F_{\mathrm {buoyancy} }=d^{2}\rho h_{\mathrm {top} }g-d^{2}\rho h_{\mathrm {bottom} }g\,$

which reduces to

$F_{\mathrm {buoyancy} }=d^{2}\rho g({h_{\mathrm {top} }}-{h_{\mathrm {bottom} }})\,$

in the case of a cube, the difference in $h\,$ between the top and bottom is $-d\,$, so

$F_{\mathrm {buoyancy} }=-d^{3}\rho g\,$

or

$F_{\mathrm {buoyancy} }=-\rho Vg\,$

where V is the volume of the cube, $d^{3}\,$

The negative magnitude implies that it is in the opposite direction to gravity. It can be demonstrated mathematically that this formula holds true for any submerged shape, not just a cube.

Changed:

The magnitude of buoyant force may be appreciated from the following argument. Consider any volume of liquid of arbitrary shape and volume $V\,$. The body of liquid being in equilibrium, the net force the surrounding body of liquid exerts on it must be equal to the weight of that volume of liquid and directed opposite to gravitational force. That is, of magnitude:

$\rho Vg\,$ , where $\rho \,$ is the density of the liquid, $V\,$ is the volume of the body of liquid , and $g\,$ the standard gravity ($\scriptstyle \approx \,$ -9.8 N/kg on Earth)

Now, if we replace this volume of liquid by a solid body of the exact same shape, the force the surrounding body of liquid exerts on it must be exactly the same as above. In other words the "buoyant force" on a submerged body is directed in the opposite direction to gravity and is equal in magnitude to : $\rho Vg\,$ ( note that here $V\,$ is the volume of fluid displaced by the body )

Reason for Edit:

The original derivation was unnecessarily lengthy and leaves the reader with no real understanding of the underlying physics. I believe this derivation is direct and elegant - and the same time lets the reader feel the physics behind it.

Special Relativity and Time Dilation.. a thought

Pertinent Article:Time Dilation

Just a thought.. it would be completely valid to presume as foundational postulate to special relativity that all objects age/move the same in space-time (dt) ^2 +(ds)^2 is exactly the same for all objects observed in a particular inertial frame.. where dt is how much i percieve the body to have "aged".. while ds is how much i percieve the body to have "moved" spatially in that interval. Distance obviously being measured in 'c' units. Needless to say, time dilation results immediately follow from that assumption. A more elegant way of understanding the result i feel than the usual textbook derivation. Lets the reader appreciate that space and time are not two separate entities but things we percieve as seperate - a limitation imposed by human senses. While the concept space-time is what truly makes sense.

time dilation( and other) results follow intuitively.. ( clock (1) at rest vs clock(2) moving at velocity v:

(dt1)^2 = (dt2)^2 +((v*dt1)/c )^2

dt2=dt1*sqrt(1-(v/c)^2)

Dilip rajeev (talk) 22:30, 2 July 2008 (UTC)

Image:Sunrise profile dilip.jpg missing description details

Dear uploader: The media file you uploaded as Image:Sunrise profile dilip.jpg is missing a description and/or other details on its image description page. If possible, please add this information. This will help other editors to make better use of the image, and it will be more informative for readers. If you have any questions please see Help:Image page. Thank you. Sfan00 IMG (talk) 11:41, 3 May 2008 (UTC)

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)

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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^{T | C | G} 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,[1] 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: [2] 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^Talk 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)

Replaceable fair use Image:1999OrganTransplantRise.jpg

Replaceable fair use

Thanks for uploading Image:1999OrganTransplantRise.jpg. I noticed the description page specifies that the media is being used under a claim of fair use, but its use in Wikipedia articles fails our first non-free content criterion in that it illustrates a subject for which a freely licensed media could reasonably be found or created that provides substantially the same information. If you believe this media is not replaceable, please:

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2. On the image discussion page, write the reason why this image is not replaceable at all.

Alternatively, you can also choose to replace this non-free media by finding freely licensed media of the same subject, requesting that the copyright holder release this (or similar) media under a free license, or by taking a picture of it yourself.

If you have uploaded other non-free media, consider checking that you have specified how these images fully satisfy our non-free content criteria. You can find a list of description pages you have edited by clicking on this link. Note that even if you follow steps 1 and 2 above, non-free media which could be replaced by freely licensed alternatives will be deleted 2 days after this notification (7 days if uploaded before 13 July 2006), per our non-free content policy. If you have any questions please ask them at the Media copyright questions page. Thank you. Do you want to opt out of receiving this notice? Rettetast (talk) 15:13, 28 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: [3], [4], [5], [6]
2. attempt at "outing", sometimes with personal attacks mixed in: [7], [8], [9] -- 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: [10] -- Please note, the user has not aggressively reinserted this after it was pointed out

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

Orphaned non-free media (Image:1993MasterLiHongzhiInterview.jpg)

Thanks for uploading Image:1993MasterLiHongzhiInterview.jpg. The media description page currently specifies that it is non-free and may only be used on Wikipedia under a claim of fair use. However, it is currently orphaned, meaning that it is not used in any articles on Wikipedia. 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 Wikipedia (see our policy for non-free media).

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August 2008

Please stop assuming ownership of articles such as Tiananmen Square self-immolation incident. Doing so may lead to disruptive behavior such as edit wars and is a violation of policy, which may lead to a block from editing. Please stop and discuss all major changes on the talk page first as it is a sensitive topic. antilived^{T | C | G} 11:41, 6 August 2008 (UTC)

I am only adding well sourced material to the article - especially from danny schechter's reports and reader on the persecution. Kindly review my edits.

Dilip rajeev (talk) 11:53, 6 August 2008 (UTC)

You have completely ignored the NPOV policy and instead presented the article solely from the perspective of FLG. The new intro is not an intro at all, and completely discredits the CCP's side of the story ("five people apparently attempted"? "which claimed the immolators were Falun Gong practitioners"??) while stating the FLG side of the story as fact by including extensive quotations from the FLG press release, creating undue weight (why no quotation from Xinhua?). You have removed the {{NPOV}} tag placed by HappyInGeneral when your edits are disputed by other people in talk page, and have been oblivious to the talk page for 3 days when you did your edits. You have removed valid section of "Beyond the Limits of Forbearance" and in general had gone against the spirit of Wikipedia of collaboration and cooperation. The article is in a much poorer shape now thanks to your POV additions and subtractions, and you still continues to ensure ownership of the article by constant edit/revert. Is that not enough evidence? --antilived^{T | C | G} 06:50, 7 August 2008 (UTC)

You can look at commentary from schechter or ian johnson all of them use the same words. The CCP media is the only source to have claimed the self-immolators were practitioners

Dilip rajeev (talk) 08:14, 7 August 2008 (UTC)

The section beyond the limits of forbearance is still there - its entirety. Merely that anoter user:asdf1234 or somebody had changed its title following my edits

Dilip rajeev (talk) 08:15, 7 August 2008 (UTC)

I am sorry that I had mistaken the removal as I saw it on the diff it had been removed, when it had been moved around. But your addition had created huge undue weight towards Schechter reports, being mentioned 18 times in the whole article, compared to 3 to the version before your string of edits. It does not matter that the source used exactly the same words, in fact the fact that you have quoted the reports puts the article to the POV of the source, which is clearly in violation of NPOV. I have put up a notice on WP:ANI on your recent disruptive edits for being completely oblivious of consensus against the change, and I sincerely suggest you to refrain from any further addition until consensus had been reached on the NPOV nature of the addition and that it does not give undue weight to one sourcee. --antilived^{T | C | G} 08:26, 7 August 2008 (UTC)

Schechter's work is one of the most comprehensive and an award winning work on the topic. It is not his own analysis, h draws upon a wide variety of sources - from RSF to beijing correspondents of international news agencies. I dont think it is accurate to call my edits "disruptive", I merely attempted, in good faith, to add structure to the article, to bring attention to analysis from schechter, wall street journal's ian johnson and also from other reputable sources.

08:34, 7 August 2008 (UTC)

• I have reviewed this matter, and the ArbCom restriction, and have blocked you for 48 hours so that the edits you have made to the article may be reviewed, discussed and amended as required - in accordance to consensus. At present I am not minded to place you on a topic ban, as I see that you have in the past properly discussed your edits, but should you continue to edit the article without reference to the considerations of other editors it may be an option. I suggest that you return to using dialogue to promote the incorporation of your preferred references. LessHeard vanU (talk) 09:14, 7 August 2008 (UTC)