The h Bar

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napstablook

03:33

This qn has been bugging me. (the condition for stability of cylindrical jets). I tried equating the excess pressure due to surface tension with pressure loss due to velocity head for A and B but it didn't work

also tried to equate rate of pressure increase due to surface tension with the rate of decrease in pressure due to faster velocity but still no luck

zed111

can someone explain how they go from eq (3.4) to (3.5) in this pdf physics.udel.edu/~bnikolic/QTTG/NOTES/MANY_PARTICLE_PHYSICS/…

napstablook

I need to understand this part of sec3.2 but since i am in high school I am very helpless about this. I need to prove $kh_0$ needs to be greater than 1. can someone explain this to me?

zed111

@napstablook what is the meaning of bar over $\delta p$

napstablook

it was mentioned to be mean pressure somewhere in this paper

zed111

03:48

so basically delta p = something times p

when that something is positive, you have exponential growth

That something has -(1 - (kh0)^2), so kh0>1

napstablook

yes but I don't get how the equation was derived

zed111

you'll have to look at eqs(9, 12, 46)

I don't know either

napstablook

irphe.fr/~fragmix/publis/EV2008.pdf

this is the paper in question. Idk if anyone can look through, but if you do pls notify me

equations of interest on pg.15

2 hours later…

123

05:49

Hello World of Physiks...

Hello @JohnRennie Sir

How virial equation of state can be written in term of power series of pressure from f(P , V , T , m) = 0, or f(P , v , T) = 0 where v = V/m.

Also what the above function meaning. What it tell us?

Slereah

"Let us consider a slightly more precise example. A common activity for school children in the UK around Easter time (a festival whose bizarre secular
incarnation is even more confused than that of Christmas) is the decoration of hard-boiled eggs, often as part of a judged competition with high chocolatey stakes. This process involves taking a topological space (an egg) and attaching some data (paint) to it."

Nihar Karve

06:05

everything is a sheaf

Slereah

06:15

"Such a sheaf is called flabby"

Slereah

06:54

"Since this is an essay being written by a Cambridge undergraduate, our rings will always be commutative with $1$"

5 hours later…

Naman Agarwal

11:41

Hi! Can anyone tell me a book which derives Noether's theorem in the way given here: en.wikipedia.org/wiki/…

I mean I have never seen the term \bar{\delta}\phi getting involved in the derivation of the conserved current.

raf

12:06

Hi, can anyone kindly tell me what's wrong with using (+, -, -, -) spacetime metric signature? Also, why does not everyone use the same one?

Nihar Karve

@raf nothing wrong with it

but let's just say you don't want to reveal your affinity for +--- amidst a crowd of -+++ hardliners

Charlie

@raf There is no inherent advantage to using that metric signature instead of the other. Different fields of physics use different signatures for various reasons.

That being said...

Mar 27 '20 at 17:51, by John Rennie

In God's own signature we write $ds^2 = -c^2d\tau^2 = -c^2dt^2 + dx^2 + dy^2 + dz^2$

raf

God's own signature?! :v

I found this also: twitter.com/BarakShoshany/status/1394278352794624001

Nihar Karve

See here and links therein for a short overview

both lead to equivalent physics of course

raf

@NiharKarve Thank you. I will check it

Nihar Karve

12:19

@Charlie did you have/are you having your exams right now?

Charlie

Nope, long story short I left my course, started getting really stressed out and made a difficult choice to not finish. Starting work in about a month from now

raf

Some days ago, I was trying to prove $p_μp^μ=m^2$, But using the signeture $(-,+,+,+)$, I ended up with $p_μp^μ=-m^2$. It felt awkward to me...

Nihar Karve

@Charlie what field are you going to be working in?

fqq

@raf that's one reason some people prefer the other choice

Charlie

It's a job at a company that does background checking etc., seems alright

I should've taken some time out of education at the end of last year when the stress got overwhelming but I did better than I expected so I went straight into this year

and when I decided I wasn't doing a PhD next year I kind of crashed, felt pretty bad about things for the last few weeks but now that I've got work lined up things are getting better

Nihar Karve

12:33

@Charlie Didn't you have to learn 3-4 years of the physics undergraduate curriculum in like half the time?

that's quite the feat

raf

@fqq I see.

Charlie

Not the whole thing, but the amount of catching up to do has been pretty large, had to start learning qed before I knew much classical electrodyanmics for example

Nihar Karve

in any case, good luck, hope everything works out

Charlie

I will still continue doing physics/math in my free time so I'll still be here bugging everyone with questions. Haven't been active here for about 2 weeks while I was feeling sorry for myself

3 hours later…

bolbteppa

15:27

@Charlie I'm sorry to hear, can be a nightmare when anything goes wrong with this stuff

Charlie

Yeah I didn't feel great for a few days, fortunately even though the job market isn't exactly great atm I managed to find a job within a few days, just got lucky I guess. Don't feel so bad now, slowly returning to doing some physics though :)

4 hours later…

Physics Meta

19:39

Q: I am being told conflicting resolutions for fixing a closed question, what should I do?

I had a question that was closed, and I was given the following instructions: Those questions listed did not provide me with the answer to my question, so I followed the advice and opened a new question that I completely reformatted. This was then in turn closed as a duplicate of my original que...

2 hours later…

M.N.Raia

21:19

Good morning/afternoon/evening/night for everyone!

First of all: I hope you all are ok, fine and healthy.

So, I got a minus sign here

In first part in RHS

Is just a matter of -F^{\mu \lambda} = F^{lambda \mu}?

2 hours later…

John T.

23:44

What's your favorite music to listen to while studying, H-bar?

I prefer jazz, classical, and most things instrumental but I also enjoy just thinking about things with other kinds of music. Some people don't really listen to any music which I find strange.

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