The h Bar

Balarka Sen

1:15 AM

@Slereah I invite you to an open challenge to prove that you're a better physicist than me.

I know everything about worldvolumes in $\infty$-stacks. Quantum field theory is a special case of that.

Semiclassical

2:01 AM

Little Jimmy Dickens - May the Bird of Paradise Fly Up Your Nose

►

also,

Balarka Sen

>:)

Cows

been coding hardcore for two days. Heading out for a short walk

user351417

2:36 AM

If we're talking about lurkers, physics.stackexchange.com/users/32015 0 rep beyond association bonus, 6.8k votes

Fawad

2:59 AM

If a body is moving towards right than the friction on it has to be towards left.

why is this statement wrong?

danielunderwood

Why do you think that statement is wrong?

Semiclassical

it's not always true, therefore it's wrong

Fawad

3:24 AM

@Semiclassical can you give an example where it’s not true?

Semiclassical

yes, I can. but i won't, because that's the point of the problem.

Fawad

Hmm for a bike moving on road,bike moves forward and friction “on three” is in motion of bike

Semiclassical

yep

more simply, an object rolling without slipping

Fawad

Ok

Semiclassical

the object is moving to the right, but the bottom of it is trying to move to the left at any instant

dmckee

4:14 AM

Well fine. It's not enough to have a lot of questions that read "How do you explain [phenomena well treated in the field picture] in terms of photons?" getting votes from people who have no idea if they are or are not either reasonable or insightful, but now ...

0

Q: How do you explain comsological redshifting in terms of gravitons?

We know that the photons from the big bang are continually being red shifted and losing more and more energy. In terms of the graviton view, how would you explain that? Where is the energy going? Are the photons emitting or absorbing gravitons? What is a good explanation without using the phra...

... we're going to get a whole slew s/pho/gravi/g which will mostly be even less insightful.

... and I just noticed that I seem to be doing my grumpy-old-man act rather more intensively than usual.

Comes natural, maybe.

danielunderwood

4:34 AM

Isn't the existence of gravitons still kind of up in the air anyway?

dmckee

4:53 AM

I believe that you can formulate a theory in those terms just fine, you just can't renormalize it.

John Rennie

5:27 AM

@dmckee it's a good question though. It's like asking how you construct a macroscopic electrostatic field from photons. The answer is of course that you don't, but then the question is why not?

NormalsNotFar

5:40 AM

If I want to consider linearized gravity but in the vielbein formalism, would it be acceptable to represent the vielbein as $e_{a}{}^{\mu}=\delta_{a}^{\mu}+f_{a}{}^{\mu}$?

where $f_{a}{}^{\mu}$ is some infinitesimal fluctuation

Secret

@Slereah ^

NormalsNotFar

If so, how may I obtain the spin connection in terms of this fluctuation (assuming zero torsion)?

Secret

@Slereah ^

(This is called Supersymmetric Ping, btw)

NormalsNotFar

5:58 AM

@Secret Sorry but are you referring to my question? I have never heard of supersymmetric ping before

Secret

ah, no, I joked about the way I use that ping. It's separate from that question

John Rennie

@NormalsNotFar no, he means Sam Lereah is our resident GR expert so he pinged him

Secret

indeed indeed

John Rennie

Sam tends to show up around 9 a.m. European time.

NormalsNotFar

Oh ok, no worries, thanks for pinging him. I'm not in a rush, so that's fine :)

Cows

6:04 AM

@NormalsNotFar hi dude, what's your deal with vielbein ?

Just curious . . . I'm stupid

but want to learn :)

NormalsNotFar

@Cows hiya, if you're talking about my specific problem atm, I am trying to linearize the curvature tensor but using the expression for $R_{abcd}$ in terms of the spin connection and Vielbein (as opposed to using the usual expression involving the Christoffel symbols and their derivatives etc)

Cows

@NormalsNotFar cool. I think it seems straightforward

ok so what I mean is. . . . I think it's one of those things you just need to sit down and calculate

John Rennie is a GR guy. . . ping him

if all else fails I might look into it

let me actually think about this

give me a sec. I am looking at wikipedia for a second

just to be sure I know what you mean clearly before I attempt to say anything

@NormalsNotFar have you attempted it?

@NormalsNotFar still there?

I want us to try to break down what you want to do into a list of smaller things then we can attempt to look at each of them

NormalsNotFar

6:20 AM

@cows To be honest I think it will be a very ugly excercise to start with the spin connection expression. It may work but only after alot of elbow grease. Right now I am just linearizing the regular Riemann tensor ($R_{\mu\nu\rho\sigma}$) and then im gonna use $R_{abcd}=e_{a}{}^{\mu}e_{b}{}^{\nu}e_{c}{}^{\rho}e_{d}{}^{\sigma}R_{\mu\nu\rho\‌sigma}$

This should be a lot quicker to prove what I want to prove, and avoids the questions I posed earlier

Cows

@NormalsNotFar ok ping me with progress, sounds like some fun stuff. To be honest I doubt that I am the most credible soul to talk about this although I find it quite interesting

so naturally for the normal baby case

John Rennie

@Cows I'm strictly a GR amateur and I can't answer Normal's question :-)

Cows

@JohnRennie I think you are selling yourself short

:)

Sir Cumference

6:33 AM

@JohnRennie I think we should bring John Duffield in to answer

John Rennie

@SirCumference the major difference between me and JD is that I know what I don't know.

Sir Cumference

@JohnRennie haha

Cup Fever

hehe

Cows

coding taxes and stuff for a point of sale app hehe

user351417

7:04 AM

JD has a book on amazon. The reviews are...

DanielSank

7:21 AM

Hi, everybody.

Slereah

@NormalsNotFar Yes.

You can find the procedure for this in Huggin's PhD thesis

"Quantum mechanics of the interaction of gravity with electrons: theory of a spin-two field coupled to energy"

although with the usual caveats of quantum gravity

It's also probably in that one book that has a decent QFT version of GR

I forget which

The caveats being the weird infinite sum lagrangian and the non-renormalizability

Slereah

7:53 AM

Overall it's probably not a great way to quantize gravity but it's probably accurate enough at tree level

Novalium Company

9:45 AM

Where can I find good circuit analysis problems with answers (for a beginner)?

Anonymous

9:55 AM

@NovaliumCompany Check the Physics Galaxy website

Novalium Company

10:18 AM

@Blue I can't find any circuit analysis exercises with answers. I only see some guys thanking Ashish or something.

Anonymous

@NovaliumCompany Hmm. Check this, this and this.

Anonymous

@NovaliumCompany There are some quizzes which you can attempt here. All of them have solutions.

Novalium Company

@Blue Ok thanks :-)

Anonymous

@NovaliumCompany Are you planning to appear for the international physics olympiad btw?

Novalium Company

Umm, if there was one... :P

Actually I'm going to find some other exercises because what you sent me is just videos and it's really hard to understand his accent and hand-writting.

Anonymous

10:25 AM

There sure are. But I guess there are some regional olympiads which you need to qualify to get to IPhO. Google for Bulgaria+physics olympiad.

Anonymous

@NovaliumCompany You can change it to "Global accent"

Anonymous

Those videos are really good btw. I learnt the whole of high school physics from there. And the sample problems are really well picked.

Anonymous

But sure, whatever you find more comfortable. You could check out textbooks like Resnick-Halliday.

Novalium Company

@Blue Ok then, I'll give it a try. Does he include exercises in his lectures?

Anonymous

@NovaliumCompany All the lectures labelled as "Solved Example-X" are exercises with video solutions.

Anonymous

10:28 AM

Where $X\in\Bbb N$ :P

Novalium Company

Oh I see. They seem interesting. I'll watch :)

Also what is linear algerbra useful for (except QM)?

Anonymous

And the whole "Advanced Illustration" playlist only consists of solved examples. But they are much more conceptually difficult compared to the solved examples in the main playlist.

Anonymous

@NovaliumCompany It's a never-ending list, really :P Almost every area of higher physics or even CS requires it.

Novalium Company

@Blue Ok, thanks for recommending it then. I'll make sure I learn it :->

Anonymous

bnr.bg/en/post/100856286/…

Novalium Company

10:31 AM

It may help me with the 2D mobile game I'm making right now :D

Anonymous

I see...your countrymates do appear for the IPhO ;)

Anonymous

@NovaliumCompany Yes! It might :)

Novalium Company

Good for them :D

Actually

I remember something about the teacher coming into the class room asking if anyone wanted to join a Physics olimpiad, but I didn't (don't remember why). So yeah. 10th grade, I'm in :)

Anonymous

Good :) I think it's a good way to develop a sound foundation in basic physics.

Novalium Company

I started this whole learning Physics, Electronics... about a year ago and look at me now :D That's a progress.

Anonymous

10:35 AM

True :)

Novalium Company

Still have a lot learn tho, and I will, because it's AWESOME!

@Blue How is uni going?

Anonymous

Uni begins tomorrow

Anonymous

It was a holiday till today

Novalium Company

@Blue How many days is ur holiday?

Anonymous

~2 months :D

Anonymous

10:40 AM

(again back to sleeping in class listening to the boring profs :P)

Anonymous

But, well, some are good.

Novalium Company

@Blue Well, if you don't enjoy it, just drop out.

Anonymous

Not an option. Lol

Novalium Company

Why?

Anonymous

By "drop out" you mean "transfer to another uni"? Or stop my undergradute studies?

Novalium Company

10:43 AM

Well, I don't know. But life is short and you should better do what you enjoy. Some decisions may not seem logical, but if you heart tell you to, then you should change something.

Anonymous

Oh, I wish I had an option :P In India there's absolutely no option of transferring to another school. And secondly, I don't have the option to drop out of uni either because I want to pursue grad school later on and it is close to impossible to get there without an undergrad degree.

Novalium Company

What's grad school?

Anonymous

Well, it's not that bad either XD

Anonymous

@NovaliumCompany Masters/PhD

Novalium Company

@Blue You wanna become a professor?

Anonymous

10:46 AM

Nope. But PhD is not meant only for "becoming a professor"

Novalium Company

Yes I know, but why do you want a Ph.D?

Anonymous

There are a lot of things which are much more difficult to learn by yourself. Better get a masters/doctorate education in those subjects. Also, your degree is (normally) a proof that you at least know the material which you claim to know.

Anonymous

Also it's pretty much impossible to lead a research group or be a part of a good research based company without a PhD.

Novalium Company

And what do you exactly want to do after the Ph.D?

Anonymous

@NovaliumCompany Something something R&D ? :P I haven't thought so far yet

Novalium Company

10:50 AM

@Blue Oh, ok then. Goodluck! :-)

Anonymous

I do seem to like machine learning and quantum computing at the moment apart from a few other areas in mathematics and physics (which I pursue as a hobby). So probably something related to those areas.

Novalium Company

11:07 AM

@Blue You here?

I don't understand what's going on with this x over here: physicsgalaxy.com/lectures/1/15/59/1122/…

Is x the voltage at that point?

Anonymous

electronics-tutorials.ws/dccircuits/dcp_6.html

Anonymous

Yes, it's the nodal voltage

Anonymous

at that point

Novalium Company

Ah, ok, I'll give it a look.

Novalium Company

11:53 AM

Guys, the node voltage method is the best thing that has happened today. Thanks @Blue for telling me about it. It seem so useful and easy!

Anonymous

Yes, it's a great method :D

Slereah

1:27 PM

Found the reason why free particles can be quantized in RQM but not if they are charged

neat

Emilio Pisanty

@Slereah is it because the charge will just shock you if you try to quantize them?

Slereah

could be

Emilio Pisanty

(if you were expecting more intelligent feedback, I'm not sure why you chose this room =P)

Slereah

The resulting Klein Gordon equation fails to be Lorentz covariant if there's an EM field that isn't $0$ in some frame

Emilio Pisanty

wat

Slereah

1:31 PM

plz mister "postdoc at ICFO"

don't pretend to be dumb :p

The word Lorentz is literally in one of your paper!

Emilio Pisanty

@Slereah that's Lorentz force, not Lorentz covariance

Slereah

I'm guessing you saw Lorentz covariance in class

Emilio Pisanty

no, I understand the content of the claim

I don't understand why it would be the case

Slereah

arxiv.org/pdf/gr-qc/0511088.pdf

derivation is p. 22

Emilio Pisanty

and I guess I also don't fully see exactly what form the KG eq. takes in that setting.

@Slereah ugh

Slereah

1:36 PM

it can take many forms because there's a bunch of actions for relativistic particles

the "physics" reason is pair production by EM fields

But it's nice to find the math reason

Emilio Pisanty

@Slereah bizarre

search.library.ucdavis.edu/primo-explore/…

UC Davis has the record

and it just sends you to arXiv for the pdf?

man, the early noughts were weird

0

Q: Is it possible to bend space 'upwards'?

According to the theory of general relativity 'space' can be bend like a fabric. Objects with a lot of mass bend spacetime like a well or a bowling ball on a stretched blanket. It (images) always look like spacetime is being 'pushed' downwards thus objects swirl around the more massive objec...

general-relativity gravity spacetime mass curvature

oh, rubber-sheet analogy. ever a source of fun misconceptions.

Slereah

too bad there isn't really any good GR analogy

even using something semirigorous like diagrams of Regge calculus

The whole Lorentzian geometry bits makes it hard to parse

user351417

There's an XKCD for everything apparently

user351417

Does anybody have any good stuff about double pendulum phase portraits?

Semiclassical

1:47 PM

as a quick image for "mass produces curvature of spacetime geometry", it's fine. But it's not the same as the math, and as such one shouldn't assume that it's going to have any value beyond that

geocalc33

@Slereah could you apply penrose diagrams to tensor networks?

Slereah

I don't know what that is

Semiclassical

@Chair I don't know a lot of people who have a mental image for four-dimensional trajectories :)

Slereah

The four dimensional part isn't terribly important

You can do GR in $1+1$ dimension just fine

And most important metrics are essentially two dimensional

But the whole negative norm thing precludes any real visualization

Semiclassical

I suspect with the double pendulum the choice of coordinates is important

just taking the angles of the two pendulums as coordinates is probably not going to give a helpful vizualization

user351417

1:52 PM

I put together the equations with the Lagrangian and stuff... but I used a sign convention which is quite different from the ones used in all the derivations I found online.

user351417

I wanted to see if my phase portraits were correct...

user351417

Because all the pictures you see online are for different, unmentioned initial conditions

Novalium Company

Guys, is the node voltage method the best/common way to analyse circuits?

Can it be applied to all circuits?

geocalc33

@Slereah you know what tensor networks are right?

Semiclassical

It's a method. Like most methods, it works better for some problems than for others.

Slereah

1:54 PM

I do not

user351417

@NovaliumCompany My rule #1 is never use mesh techniques

Semiclassical

I've heard of tensor networks in passing, with the context being certain kinds of calculations in condensed matter

Novalium Company

If I want to analyse this circuit using the node voltage method and understand what's going on, can I?

Semiclassical

c.f. physics.aps.org/articles/v2/90

Novalium Company

(Because I have no idea what's going on right now)

Slereah

1:56 PM

I mean there's nothing special about Penrose diagrams, you can do a conformal compactification for many manifolds, but I don't know hown this relates to tensor networks

Semiclassical

that said, there's no particular reason why a method applied to quantum calculations should have anything whatsoever to do with spacetime diagrams

I'm not going to say there's no context where they can overlap, but they're basically different objects.

Novalium Company

Guys, is it worth even trying to make some sense of this circuit? It there any logic to it or I should just remember that it's an audio amp?

Semiclassical

I think once you get to a circuit like that, you'd need someone with a bit more EE training to understand its behavior

the nodal analysis should still work---it's just a statement about the electric potential at different points

Novalium Company

Well, I'm trying to get to the level where I understand circuits like these.

Semiclassical

but once I see a transistor or a diode I basically don't have anything insightful

but node/mesh analyses are just ways of assigning current and voltage variables to the system, and to figure out what constraints are imposed by Kirchoff's rules

Novalium Company

2:00 PM

Yes, but how can I make sense of this circuit? Should I just follow the current and voltage and see how they get changed by the circuit or?

Semiclassical

Like I said, once a nonlinear circuit element shows up, I don't know what guidance to give

at a certain level of complexity, I suspect one either has to 1) break the circuit down into simpler equivalent portions, or 2) simulate it

But this is something for an EE person. The typical physics-level understanding of electronics is not sufficient

Novalium Company

Then I shall ask Blue :-)

geocalc33

@Slereah I guess you could treat the intersections of space and time curves in the penrose diagram as 4-tensors

Slereah

what

geocalc33

I don't know I was just thinking about the hyperbolic tensor network called MERA

Semiclassical

2:03 PM

I believe the phrase "not even wrong" applies here

geocalc33

in a tensor network a 4-tensor is a tensor/node with 4 edges coming out of it

Slereah

I don't know enough about tensor networks to tell you much

geocalc33

okay

Semiclassical

I mean, there are papers with both "penrose diagrams" and "multiscale entanglement renormalization ansatz" in them. e.g. this paper: arxiv.org/pdf/1709.03513.pdf

but I have nowhere near enough expertise in either to want to touch that

Slereah

also from what I can see tensor networks are for quantum states

Penrose diagrams are for global topology

Semiclassical

2:14 PM

yeah

Slereah

I don't really see the link between the two

Semiclassical

the places where I see them being linked is in the context of holography

Slereah

I guess what that paper does is just map the nodes from the original spacetime to the compactified one?

So it's basically just a tesselation in hyperbolic space

Semiclassical

right.

in that context, though, there's a reason they phrase it as "de Sitter - MERA correspondence" rather than "penrose diagram - MERA correspondence"

beyond the fact that the former sounds better, it's also just true that what's essential is not the use of a penrose diagram but that one is describing de Sitter space

Slereah

Also wait

From some papers, I am also seeing some analogies with Penrose tensor notation

is that what you mean by tensor diagrams?

"Tensor networks come with an intuitive graphical language that can be used to reason
about them. This diagrammatic language dates back to at least the early 1970s by Roger
Penrose"

that is yet another thing

Semiclassical

2:21 PM

yeah, there's definitely a link there

historically anyways

but, I mean

there's a lot of stuff named after penrose

and just because they're named after him, doesn't mean they have anything deep in common

Slereah

or anything

penrose tensor notation is just an ugly notation nobody uses

not even him

Semiclassical

lol

people have used the notion of graphical notation in QM beyond him, to be fair

though "people" != "most people"

I've mostly heard about it in the context of quantum computation stuff

also something something category theory

Slereah

oh there's plenty of graphical notations used

just not penrose notation

Except for that one book

Semiclassical

right

road to reality?

one of his technical monographs also has an appendix on diagrammatic notation, but uh

appendix

Slereah

No

books.google.fr/…

this book

Semiclassical

2:26 PM

oh, right

Slereah

it's the only one to use it extensively

Semiclassical

yeah

what it seems like is that the idea of diagrammatic notation works great for stuff which is essentially quantum

but not so much for anything else

Slereah

i had to use the notation

It looks all nice and good on a computer

but once you have to deal with rank 4 tensors on a board

it's a bit of a mess

Semiclassical

I like the idea of it, but

in practice it mostly just seems superfluous

about the only time I use it for anything productive is when I want to do a bunch of cross-products and get that down to something simpler

e.g. $(a\times b)\cdot (c\times d)$

that said, it's never motivated me to learn a whit about categories

Slereah

Category theory isn't terribly well presented in most books

Semiclassical

2:39 PM

that I can believe

plus, the ways in which category theory is valuable to a pure mathematician needn't be the same in which it's valuable to other disciplines

bolbteppa

@Slereah you mean 'why free particles can be quantized with $i \partial_t \psi = \sqrt{\mathbf{p}^2+m^2} \psi$'?

Slereah

it's the whole thing about why QFT is necessary

You can do BRST quantization of a relativistic point particle, but you can't do it in a Lorentz covariant way if it's charged

bolbteppa

As in, why you can't just take that equation?

Looks like that's what he was doing, "I have discussed the use of different hamiltonians: the non-relativistic case as well as the square-root relativistic one, with or without interactions"

Semiclassical

if I act with $i\partial_t$ on the left twice, I get $-\hbar^2\partial_t^2\psi =(\mathbf{p}^2+m^2)|\psi = -\hbar^2\nabla^2\psi+m^2\psi$ which is just the K-G equation

bolbteppa

P&S discuss the propagator for such a Hamiltonian in the beginning as well

Slereah

2:46 PM

yeah unfortunately he uses the Goto-Nambu action a lot

Which doesn't parse all that well

Polyakov all the way

also apparently you can do classical mechanics in a parametrized way

why would you I don't know but you can

bolbteppa

Wait is Klein-Gordon the 'Polyakov' of that thing

Semiclassical

K-G is what's appropriate for a spin-0 relativistic point particle, right?

Slereah

The classical action comes in many forms

bolbteppa

You can't just say it's the Polyakov because there are operators in the square root acting on a field, not a square root of fields

Slereah

Nambu-Goto is $$S = -m\int \sqrt{\dot{x}^\mu \dot{x}_\mu}$$

bolbteppa

2:49 PM

Yeah KG is the spin-0 relativistic point particle equation

Slereah

While Polyakov is $$S = \int \frac{1}{e} \dot{x}^\mu \dot{x}_\mu - e m^2$$

Both produce the same quantum theory

which obeys the KG equation

bolbteppa

It's nuts that putting the canonical commutation relations on that action leads to Polyakov as a constraint

enumaris

5:18 PM

beans > nuts

just fyi

ACuriousMind

True, can't make refried nuts

danielunderwood

+1

enumaris

indeed

danielunderwood

Refried nuts sound disgusting

@enumaris are CNNs used much in NLP? I had the thought last night and it seemed like it may be n-grams on steroids. I found some people attempting to do it, but didn't know if it was a common thing

enumaris

yeah afaik CNNs are used in Spacey

Spacy

they use deep CNNs for their models

danielunderwood

5:26 PM

Ahh neat. Are you building models yourself or is it mostly building functionality out of existing libraries?

enumaris

I augment the models from existing libraries

e.g. Spacy does not have named entity linking so I write my own algorithm to do that. It has a simplistic word vector based document similarities - and I augment it with TF-IDF.

I also blend together functionalities from NLTK with those from spacy

But I don't like build my own Named Entity Recognition or Part of Speech tagging models or something pre-existing like that. It seems like that would be a waste of my time since NLTK and Spacy have spent a ton of time working on their models and have access to a lot more data than me.

I do plan on retraining spacy models with my own data though - but that's a planned improvement for the future :D

danielunderwood

Oh awesome. Where do you figure out how to augment the models? In my little bit messing with ML, I could implement a model from a paper but never really understood how to improve it. Is there a methodical way to do it or do you just get an idea and try it out?

And I think updating a pretrained model with new data is pretty common. I think there's even a word that people use that I don't quite remember

And do you use all of your data or try to blend in open datasets?

Although I suppose named entities could be specific to your application

enumaris

5:49 PM

o.o

For augmenting the models, that's just stuff I need to get done and if Spacy or NLTK doesn't have it, I just write it myself.

By augmenting I mean doing stuff on top of those models. I don't actually mess around with the models themselves there. So I don't have to mess around with spacy API for those parts.

I don't do it methodically, I mostly see a need and then fill that need lol.

danielunderwood

Ahh well that's the only technique I've heard of so far lol

enumaris

My data is unlabled so I can't easily use it to improve an existing Spacy NER model. But Spacy has a tool called Prodigy that helps you train Spacy models using prexisting unlabled data

That one is not open source though, so I have to first get someone to buy it lol

danielunderwood

Huh I didn't even know you could train on unlabeled data

enumaris

You can't

Prodigy is a labeling tool essentially

but it streamlines the process in a such a way as to make it easy

rather than me going in manually to each of my documents and hand labeling the Named Entities (where they are and stuff), prodigy uses the existing model to "predict" something and then asks me if its prediction is right or wrong.

danielunderwood

Sounds like you need an intern that just labels stuff all day lol

I did once have an idea to create a website for crowdsourcing data labeling. Don't know that that would work in cases that you have private data though

enumaris

5:56 PM

yeah, I think the labeling is probably gonna be an intern job

Mozilla used crowdsourcing to get labeled speech to text data for their deepspeech program.

They call it project Open Voice

You can check it out

Semiclassical

in academia, there's Zooniverse

danielunderwood

Oh cool I'll have to check those out

Zooniverse kind of sounds like a kids' tv show

enumaris

indeed

I can't crowdsource my data labeling though

it's private data lol

Semiclassical

yeah, that's a bit difficult

enumaris

prolly just get an intern at some point...

enumaris

7:37 PM

mmmm this new tableau dashboard I developed is actually looking pretty nice imo

danielunderwood

Gotta be better than my current work project. If anyone ever asks you to work on an android project, you should run far far away

gateprep

Solve question 4 fast pls

I just want the entire solution with the steps

urgently pls

danielunderwood

2

gateprep

no question 4..

I want the answer along with the steps

enumaris

can't view images

but generally we are not problem solving machines lol

danielunderwood

7:49 PM

Sure. Just sit down with a pencil and paper

gateprep

Just do this problem pls

I am stuck up

Is anyone doing it?

enumaris

I can't even see it lol

gateprep

@danielunderwood

danielunderwood

Nobody here is going to do your homework. Getting yourself unstuck is generally how you learn the most.

5

gateprep

Ok do this problem pls

enumaris

7:52 PM

hmmm

there's an integral involved

badum-tiss

gateprep

ok pls tell me step by step

explain me

@enumaris are u serious.. for the problem?

enumaris

Pretty sure there's gonna be an integral in there somewhere

gateprep

apart from that

enumaris

draw some differential mass elements, then integrate the kinetic energy over all the mass elements?

gateprep

how to get to the diff equation tell me

enumaris

7:59 PM

See my previous comment

Avnish Kabaj

@gateprep take an element at r distance from the center of dr thickness then proceed?

enumaris

draw a differential mass element, it's moving down the pipe at velocity $u$ depending on where it is in terms of $r$, then integrate the mass elements over all of $r$.

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