The h Bar - 2013-07-28

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1:19 AM

@tpg2114 here sengpielaudio.com/calculator-airpressure.htm he says that elevation does not affect c, but if air pressure is a term?

1:37 AM

Pressure isn't a term anywhere

The P in your equation for h is constant

c = sqrt(\gamma R T) which doesn't include pressure

well, p is defined at sea level

right?

Yes

so consequently if we are not at sea level p is less

right?

Yes, but the variations in pressure are quite small

For atmospheric conditions anyway

ok, so its not zero its negligible

1:43 AM

Yeah, the more humid it gets the more it matters

But even then, we're talking like 0.1 m/s differences

So like 0.02%

For example, using that calculator you linked -- 100% humidty at 96.325 kPa gives 344.68 m/s while at 101.325 kPa it's 344.62

96 kPa is like... worst hurricane ever kind of low pressures

At sea level anyway

engineeringtoolbox.com/air-altitude-pressure-d_462.html

There is an equation for the dry pressure with altitude if you need to include that too

BTW do you feel like giving your name/dept? i will acknowledge you if I get the mathcad sheet working. If youre uncomfortable giving it here just email donovan digital at gmail (one word lowercase)

Tim Gallagher, Department of Aerospace Engineering, Georgia Institute of Technology

Graduate Research Assistant officially

k cool. i might work on some other stuff but I'll definitely get back to it in a week or 2

No worries. I probably won't be online much this week anyway... I'll be at track national championships in Indianapolis with an athlete I'm coaching

K cool thanks again for all your help and good luck

1:54 AM

If you do need help with something this week you can always email me

It's first name dot last name at gatech.edu

Thanks again, I'll probably ask you to doublecheck the whole calc (this is maybe 60-70%) but I'm tired of this frankly. I want to do some other work briefly.

I'm sure the worst part is you know others have done it, like that link you sent :)

yea more than once :/

But not in mathcad :)

7 hours later…

9:22 AM

You are my LaTeX, my only LaTeX. You make things pretty, that Word will slay. You'll never know, dear, how much I love you. So please don't take, my LaTeX away.

7

user image

Prof gave us a newtonian mech assignment for some weird reason, but allows online submission. Fun! :D

/needs to learn tikz

6 hours later…

3:38 PM

0

Q: The tag "virial theorem"

The tag virial-theorem has just 2 questions attached to it, and I haven't, to date, seen a question that could accomodate it. Should it be just gotten rid off?

discussion tags tagging burninate-request

4:31 PM

@ManishEarth Are you still working on the thing with the teaser?

user54412

4:41 PM

@ManishEarth I never wondered what you'd sound like drunk, but now I know anyway

5

5:31 PM

@ChrisWhite LOL

@Gugg It's part of an assignment due tomorrow. While we're allowed to discuss it and I doubt the prof would mind if I posted a related question on Phy.SE, I'd prefer to wait for the due date to pass by before posting anything :)

@ChrisWhite I basically was amazed by the awesomeness that LaTeX can produce ^.^ . I've made a handful of documents in LaTeX, but never one for submission, and I haven't used stuff like wrapfig much till now

5:49 PM

@ManishEarth You live in hostel?

?

@ManishEarth I want to ask, how compulsory is it to actually reside in hostel, as mentioned on the websites of iit's and other such government institutes of india? I hope you can help me in this

@Iota Umm, yeah

Do you know about CBS? Centre for excellence in basic sciences,mumbai?

How strict are they regarding the compulsory stay in hostel rule ? How strict is iit ?

I am actually a resident of mumbai.

@Iota I think if you live in a certain zone near iit, you don't have to stay in a hostel. But it's pretty painful to do so as lectures and quizzes can be at any time of the day or night, and all the activities have a similar schedule. If you really want to get the full benefit of the insti, you have to stay here.

@Iota So am I

5:52 PM

I have gotten into CBS

Staying in a hostel as opposed to what, I wonder.

@Iota chat.stackexchange.com/rooms/9859/room-for-manishearth-and-iota

@Gugg Nearby. Apartments and all

6:17 PM

afternoon

hey :)

hows everyones weekend been?

still going on

but was fun

good to hear! get up to much?

Messed around with LaTeX, gave an informal talk on Bitcoin (which led to some great discussion), and was doing some stuff related to the freshman technical activities (I'm part of the technical activities board of my uni)

Also am trying to write a MediaWiki extension

6:19 PM

ah bitcoin, trying to explain that to people can be painfully difficult

Yeah, but it was only 20-ish people. All friends

the main response i get when trying is "but none of it is real, its all pretend money and value"

We're basically seeing if we can hold such informal talk+discussion session on a topic of individual interest (to make other people aware and interested) every weekend, and as no one else volunteered for the first talk, I did it. And it went really well. :D

@RhysW That wasn't really the issue here, we've all had an economics course and know that money is basically liquid stuff

(liquid in the economics sense, not in the phase sense :P)

:P thanks for clarifying

But there were other questions about misuse and stability and whether the benefits outweigh the bad parts

6:21 PM

just to check, liquidating my assets should NOT involve me using a blender right?

@ManishEarth for me most people sturggled to accept that the value of a bitcon changes, despite the fact all real world currencies do it too

@RhysW Ah

There's an SE for that :P

be back in a while

@ManishEarth i dont think thats the right kind, but i think we just created a new meme

First there was "theres an app for that" now there is "Theres an SE for that"

2

"Colder days mean the air density is greater." Isn't that patently false? Or am I confused?

golftips.golfsmith.com/…, section Air Temperature.

Versus:

The density of air, ρ (Greek: rho) (air density), is the mass per unit volume of Earth's atmosphere, and is a useful value in aeronautics and other sciences. Air density decreases with increasing altitude, as does air pressure. It also changes with variation in temperature or humidity. At sea level and at 15 °C, air has a density of approximately 1.225 kg/m3 (0.0023769 slugs/ft3) according to ISA (International Standard Atmosphere). Temperature and pressure The density of dry air can be calculated using the ideal gas law, expressed as a function of temperature and pressure: : \rho = \fr...

OK, so I was wrong! Apologies! :)

6:55 PM

@RhysW It's an old meme. Not a new one. We use it all the time in TL :P

7:08 PM

Damn, probably will miss this week's chat session >.<

2 hours later…

8:52 PM

@ManishEarth ruin my fun why dont you :P i cant get into TL anyway so xD i will re invent it :P

1 hour later…

user54412

10:00 PM

user image

user54412

sometimes one can't help but approve of snark

2

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