The h Bar

@ManishEarth: If I'm on a lift accelerating upwards and I feel a force pushing down on me. Is that due to gravity or me bieng accelerated ... or both?

ManishEarth

@Nick both

Nick

So, F = (g+a)m ?

Anonymous

@Nick yes...........................

Nick

Totally idiotic Question: What would you take as the sign for gravity?

Anonymous

9:39 AM

@Nick It's just a convention.

Anonymous

You could make downwards negative.

Anonymous

in Monkeys and Donkeys, 22 hours ago, by Stack Exchange

DIMension10 has removed DIMension10 from the list of this room's owners.

Nick

Yeah but then, if I'm accelerated more than the magnitude of gravitational acceleration, The equation telles me there's an upward force on me.

Anonymous

@Nick still a convention. If you take downwards as negative, then the normal force would be +Ve.

Nick

@DIMension10: Either way, the equation tells me that there is a force acting upwards, regardless of convention, when acceleration is greater than g.

Anonymous

9:46 AM

@Nick Because it already uses the convention in which upwards is positive.

Anonymous

@Nick Well, if F, a, g, and are vectors, then it should be F = (a - g) m .

Nick

Oh, that explains A LOT.

My logic's faulty. I need to get it replaced.

Anonymous

@Nick And so, F is positive if a > g, remember, g is negative and a is positive in the upwards is positive convention.

Nick

Does anyone know of places that sell positronic brains?

F= (a+g)m for when I'm going dowwn then.

Anonymous

@Nick No.

Nick

9:51 AM

That makes absolute sense

Anonymous

It's still the same.

Anonymous

(a - g) m

Anonymous

Because then a is also negative.

Nick

XD Vectors.

Thank you. I'll keep that in mind.

Oh, and also, has anyone here heard of negative absolute temperatures?

Anonymous

►

ManishEarth

9:54 AM

@Nick negative temperature? Yep.

Anonymous

Hey, youtube videos embed here

ManishEarth

Negative temperature

[[File:ColdnessScale.png|right|thumb|[http://www.bipm.org/en/si/ SI] temperature/coldness (1/kT) scale.]] In physics, certain systems can achieve negative temperature; that is, their thermodynamic temperature can be expressed as a negative quantity on the Kelvin or Rankine scales. In colloquial usage, "negative temperature" may refer to temperatures that are expressed as negative numbers on the more familiar Celsius or Fahrenheit scales, with values that are colder than the zero points of those scales but still warmer than absolute zero. By contrast, a system with a truly negative tempera...

Nick

The thumbnail embeds.

Why are they hot?

Anonymous

@Nick . read the wp article that Manish Earth sent you.

ManishEarth

temparature basically has a more fundamental definition than the usual equilibrium one

Nick

9:57 AM

It's so frustrating to have a browser that lags as much as mine does.

Anonymous

Nick

@Manish: The thermodynamic Beta.

ManishEarth

yes that

Nick

Oh and the boltzman's constant. That allows the conversion of temperature into energy? Wed Thu Fri ?!

ManishEarth

sort of

I prefer to look at it as the bridge between stat. thermoD and normal thermoD

Nick

10:05 AM

As a person with absolutely no exposure to thermoD, I for a second thought that Temperature could thus be converted to mass. XD

@Manish: Was that funny?

ManishEarth

sorta :P

Nick

It must disgust you to even hear of such a fallacy.

Apologies

Ooh, here's an exercise in vocabulary, What's the opposite of a fermion?

ManishEarth

boson?

hmm

fermioff?

2

Nick

XD

Anonymous

@Nick A squareheadon. : )

Anonymous

10:16 AM

(A pun on Fermi's head)

Anonymous

or a feaddon.

Anonymous

(A pun on the wiki editing shortcut for "removal")

Anonymous

Or a feryuon.

Nick

I'm searching for the reason spin is half. And in my journey I found the sentance "Fermions, the particles that constitute ordinary matter"

Anonymous

Or a nutfermion.

Anonymous

10:18 AM

or a fermyon. No idea how that is relaevant. Or if it is real;' word.

Nick

@Dimension10: His head isn't that weird.

Anonymous

Or a Paulon.

Anonymous

Or a Diracon.

Anonymous

Or an Enricoon.

Anonymous

10:22 AM

physics.stackexchange.com/posts/70913/revisions

Anonymous

-10

Q: This is a sandbox

an edit has been made to this post; click to load. ' http://i.stack.imgur.com/gVDZr.png This is a sandbox* You can use this question as a formatting sandbox (if you can edit Community Wikia questions), and you can post answer...

support formatting

Nick

@DIMension10: Well, that ingenious head caused the greatest innovations in statistics and physics. Most smart people have weird heads.

Look at Einstein for example he "rode on an electron". That should explain his hair.

Anonymous

@Nick Wiki Pedia even has an image "File:Albert Einstein Head.jpg".

Anonymous

en.wikipedia.org/wiki/File:Albert_Einstein_Head.jpg

Anonymous

10:45 AM

Anonymous

Interchanged Einstein's and Newton's hairs.

Anonymous

Both are pretty weird.

UV-D

@DIMension10 Einstein looks like a member of a 70's rock band

Nick

hese men could envision the universe for what it is... but never in their lives would they have expected photoshop.

2

Anonymous

@Nick No, MS Paint. : )

UV-D

10:51 AM

even worse!

Nick

XD

No one expected that

UV-D

nor the Spanish Inquisition

Anonymous

@UV-D microsoft expected that.

Anonymous

and that's why they made MS paint.

UV-D

@DIMension10 iwould not be surprised at all

Anonymous

10:53 AM

... to let me vandalise that too .

Anonymous

That's an Einstein + some monarch related to Spain + a chimpanzee.

Anonymous

Ok, now since when was this a Photography chat room?.

Anonymous

[photo.se] = Photography

Anonymous

11:32 AM

Anybody knows how I can find all the close votes on a question (likely to be using Data.SE)?.

Crazy Buddy

12:22 PM

@ChrisWhite Try this one: "Why does E=mc^2?" by Brian Cox.

Totally lay-introduction to relativity & spacetime ;-)

(wouldn't be boring)

@ManishEarth Irodov? o_O

ManishEarth

nono

<number> challenging physics puzzles or something similar

Nick Kidman

what's going on here?

Crazy Buddy

@ManishEarth ah... Think deeply. If you get the name, don't forget to tell me :P

@NickKidman Lay-book suggestions for Chris ::)

See the starred msg

We have some confusion in book policy. (No?) which is why Chris is asking in chat :D

Nick Kidman

12:54 PM

A book on how to get layed?

Crazy Buddy

1:23 PM

@NickKidman Would you need a book for that? (or do ya haz one?)

Kazi arafat Ahmed

2:02 PM

Can any one explain to me what is meant by integrability or integrable system?

Arc676

2:13 PM

Hi all!

Anyone here familiar with causality?

ManishEarth

Got an adapter for the speakers I brought from home.

First order of business: Play Coldplay's Atlas on it for the "explode" bit

Kazi arafat Ahmed

2:32 PM

What are your problem with causality?

@Arc676

Crazy Buddy

@ManishEarth What??? You brought the speakers without adapters? o_O

ManishEarth

nah

Old pair of speakers

Crazy Buddy

ah...

ManishEarth

Not those annoying pc speakers, really nice and compact and powerful clamshell-type speakers

Arc676

@KaziarafatAhmed I mentioned a topic here yesterday about a whether or not certain reactions would violate causality. I asked a question (found at physics.stackexchange.com/questions/83513/…) and got an answer stating it would violate causality

Crazy Buddy

2:34 PM

@ManishEarth Oh... I've got 2.1 :D

Arc676

I had another idea for a diagram, but I wasn't sure if it would have the same problem

Kazi arafat Ahmed

I am sorry, I didn't studied feynman diagram.
Do you have any idea about integrability or a integrable system @Arc676

Arc676

No, I have little experience in physics

Kazi arafat Ahmed

Where is your interest?

Arc676

I like particle physics because understanding how stuff works on a picometer scale has proven to help me understand how stuff works on a much bigger scale

Kazi arafat Ahmed

2:44 PM

http://en.wikipedia.org/wiki/Causality_(physics) @Arc676
causality means the relation between cause and effect.
If there is a cause then there would be an effect.
Cause is proportional to effect.
@Arc676

Arc676

Did you read my question?

Kazi arafat Ahmed

Can any one explain to me what is meant by integrability or integrable system?
@CrazyBuddy

Crazy Buddy

@KaziarafatAhmed I can't say "anything" other than, "Integrable means that it can be integrated" :D

Arc676

@KaziarafatAhmed If you read the question you will see that a certain Edward replied stating that the new up-quarks will not be able to interact with the old ones. In this chat, someone else stated that they WOULD be able to interact with the old ones without violating causality

Anonymous

4:02 PM

5 hours ago, by DIMension10

Anybody knows how I can find all the close votes on a question (likely to be using Data.SE)?.

dj_mummy

5:09 PM

Hello people. I have a question too short for this site, so I'll ask it here. Why is it that we don't see at-least a few objects in the universe of arbitrarily high energies (close to Planck length)?

ManishEarth

@dj_mummy define "object"

Astrum

8:48 PM

Anybody taken a look at Landau "Mechanics"?

Jack M

9:42 PM

hi

I was wondering if anyone would mind answering a small question I have on electrostatic potentials

it just seems odd to me that the potential of a point charge should be equal to the norm of the electric field, multiplied by the distance from the point charge

so I'm wondering if I understand it correctly

hwlau

10:17 PM

@Astrum Many here

@JackM It is just because V~1/r and E=dV/dr ~ -1/r^2, so your relation

but it is only for single point charge

Jack M

okay, that's roughly what I was thinking

Astrum

10:58 PM

@hwlau how'd you like it? It seems really terse. I have however heard that it presents classical mechanics in a very elegant mathematical form.

hwlau

11:16 PM

@Astrum It's good and terse. I would not say it is 'very' elegant, as it mainly presents some concept and write down the results, so it is easier to read after you have background. And the starting appoarch is different from other mechanics book (not from newtonian mechanics)

Jack M

11:38 PM

sorry I never said thanks

anyway goodnight

Astrum

11:48 PM

@hwlau I only had the chance to take a glance at the first couple pages, it starts off right away with deriving Lagrange's equations. How would you compare it to something such as Goldstein? Goldstein seems awfully long to me, and appears to cover a lot of topics that were covered in a "lower" level book, such as K&K

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