The h Bar

MEEC just has a lot of people who are there because they did not know what to pick

that bothers me

1:01 AM

I understand. that changes as the year progresses though, some leave, some change, etc

Also, what's up with IST's evaluation system

it's all just exams

there are barely any projects

you can't even get extra credit on any class

Regarding MEFT, one of two things happens: Either people wanted to go to Aerospace engineering but the average didn't let them (not an issue this year anymore ^^) or they thought they wanted physics and then realize they don't and leave... usually only ~45-50 of the initial 60 remain

60? MEEC has like 220 people :(

Well, I don't know about MEEC, but I have plenty of projects all the time

I don't :|

1:04 AM

Perhaps it is in part because you don't learn programming in first semmester if I'm not mistaken

but you must have them at SD, no?

Yeah, SD lab is hell on earth

and Chemistry lab is a meme, it's not a project

ahahah, oh yeah, Vivado and stuff

yeah, it's commonsense, chemistry sucks xD

Don't say that name next to me, I get triggered :P

My general chemistry course was absolute shit

I passed with a glorious 10.3

mine too... You're not alone at all aahahaha

Linear Algebra was really good

the prof was great

1:06 AM

I mean, I had 15, but if you ask me, I didn't learn that much

How's he called?

Lina Oliveira

dmckee

@ACuriousMind I chickened out on putting that one on my office door. My tenured colleague put t up with glee in his eyes.

and Rosa something

btw, about the extra credits in classes

I'm glad that isn't a thing

You shouldn't be "forced" to go to classes

Hm? I'm not talking about mandatory attendance

I'm talking about doing projects that you don't have to do

to be able to get extra credits if you chose to do them

1:08 AM

ah

that's not so common, yes

I got good grades in SD, that was a surprise

Only had two subject in which it happened like that

btw, you must have heard about him, no?: 1drv.ms/i/s!AvCx1o7OEY-Yg2Ws5IOXL4nBGFyl

Huh? Who is that?

A linear algebra teacher, usually gives classes to MEEC

Well, gtg, have to rest for the exam xD cya

AH

I KNOW HIM

His exams were hard AS FUCK

1:10 AM

see? xD

@Kelthar Good luck at the exam tomorrow!

thanks! cya around :) By the way, sent you a friend request on fb, I'm Diogo

@Kelthar Sweet, see ya!

DanielSank

3:00 AM

We need a thorough Q/A on how a laser works.

3:19 AM

iamawesome.com

obe

3:55 AM

@DanielSank do it

5:56 AM

@BernardoMeurer actually I can only find one spare. I must have given the other away.

I was using the spare amp on my PC for gaming, but it was more hassle than it was worth, which is why it's now packed away in a storeroom.

6:18 AM

→ 1 message moved to Trash

7:01 AM

@JohnRennie good morning (^ム^)

why tensile young's modulus of bone is more than commpressive

@Ramanujan I have no idea I'm afraid. I don't know anything about bone and its mechanical properties.

user228700

7:30 AM

@JohnR: Good morning :-)

how to find a minimum of $x^2+y^2$ under the condition $x^3+xy+y^3=1$

@Kaumudi.H Morning :-)

user228700

@Ramanujan You do realise that he's not an answering machine, yes? Would you go up to somebody and ask them a random question without any context whatsoever?

user228700

Ah, u edited your message.

Actually I can't remember how you do constrained minimisation problems like that ...

7:34 AM

> I hang around in the chat room and I'm happy to answer questions there as well. Just ping me if you want my attention.

user228700

@Ramanujan Well, sure but why should that deter you from being nice?

Being nice?!?

user228700

Yes, why are you shocked?

I think Kaumudi just meant it looked like the question came out of nowhere, rather than saying something like "Hi John, are you busy? If not could you help me with this?"

user228700

^ Exactly.

7:37 AM

But I'm not fussed and I would help you with the question if I could remember how do do it.

Sadly, much of the maths I learned at school I've since forgotten.

user228700

@JohnRennie I know that you don't mind :-) Still, it's not very nice to do that and I simply wanted to point out that to him.

I would take the equation $x^3+xy+y^3=1$ and write an expression for $x^2+y^2$ at every point along the curve, then minimise it. But I can't immediately see how to do that for an expression you can't easily write as $y=f(x)$.

Kaumudi have you done that sort of constrained minimisation?

So derivative is not involved? Like f'(x)=0

user228700

@JohnRennie Not that I can remember but I'm trying...

Constrained optimization

In mathematical optimization, constrained optimization (in some contexts called constraint optimization) is the process of optimizing an objective function with respect to some variables in the presence of constraints on those variables. The objective function is either a cost function or energy function which is to be minimized, or a reward function or utility function, which is to be maximized. Constraints can be either hard constraints which set conditions for the variables that are required to be satisfied, or soft constraints which have some variable values that are penalized in the objective...

7:40 AM

@JohnRennie thanks for link

Actually it was question on maths SE

math.stackexchange.com/questions/2107048/…

Nevermind someone has answered

Ah, hang on.

user228700

@JohnRennie Oh, no, I have. The nature of the constraint sort of threw me off but yes. hang on...

$x^2 + y^2$ is just the distance from the origin.

So the question is effectively at what point does the curve $x^3+xy+y^3=1$ come closest to the origin.

Nice!

user228700

^^ Yep, very nice :-)

7:44 AM

Hi Pato. I don't think you can post here until your rep reaches 20.

I assume you're interested in discussing the difference between QFT and the Schrodinger equation.

user228700

Hmm, what does the equation $x^3+xy+y^3=1$ represent? .__.

@Kaumudi.H a curve

user228700

Dude.

user228700

What kind of curve is my question!

@Ramanujan I think the general approach to questions like that is to use Lagrange multipliers. In this case i would start by sketching the curve and the answer should be obvious.

7:52 AM

user228700

Thanks :-) How the heck are we to determine which point is farthest from the origin?!

There is no point on that curve farthest from the origin.

OK so the nearest point to the origin is when $x=y$ in which case you need to solve $x^3+xx+x^3=1$ to find the value of $x$ and therefore $y$. Then calculate $2x^2$

user228700

Ah, ur question is minimum, not maximum.

@JohnRennie I don't think so.

user228700

7:55 AM

@JohnRennie How did u ascertain that the point would lie on the line $x=y$?

It seems the points on the x and y-axes are nearer than the bulge

just because it's symmetric through $x = y$ doesn't mean it has to have the minimum there. just a local extremum

Well that's easily calculated.

user228700

What kind of a function is $x^2+y^2$ anyway?

well what does it equal?

$r^2 = x^2 + y^2$

7:59 AM

It measures squared-distance of origin from $(x, y)$.

user228700

Alright, I'm going to move on from this. Multi-variable calculus is not there in my syllabus.

It's a paraboloid centred on the origin

paraboloid = parabolic shaped bowl

@Kaumudi.H yeah,i was also just looking :D

too bad, multivariable calculus is the real deal

@JohnRennie i seem to be missing something there john, isnt that a circle

not a paraboloid

8:00 AM

For a fixed $r$, sure

user228700

^

Graph of $z = x^2 + y^2$ in R^3 is paraboloid

Graph of $z^2 = x^2 + y^2$ on the other hand is a cone.

user228700

@Balarka: Do you regularly work with complex numbers?

@Kaumudi.H it comes up a lot in physics, especially upper div

@BalarkaSen I get $x \approx 0.6573$ when $x=y$ and that gives $z \approx 0.86$ i.e. $\lt 1$.

8:01 AM

not regularly, but I do.

user228700

@Skyler Yes, I know :-)

user228700

@BalarkaSen Well, I found an excellent series about them on YouTube. I dunno if this series is far too basic for you but here:

@JohnRennie Hmm. You seem to be right that the min is on $x = y$. Strange!

Imaginary Numbers Are Real [Part 1: Introduction]

Thank you, thank you :-)

user228700

►

8:04 AM

No,minimum can be at more than one point,it may be guess until he prove why …

user228700

There are a total of 13 videos, each one more complex than the last. So, you might want to skip the first few...

@Kaumudi.H I don't really want to watch it though. But thanks.

user228700

OK.

personally I like the geometric visualization of complex numbers on the number plane

@Ramanujan it's obvious from the graph that there is only one minimum

@Kaumudi.H I imagine Balarka Sen probably knows about complex numbers already :-)

8:05 AM

@JohnRennie but does he complex analysis?

user228700

For anybody else who is interested but is also sceptical about whether or not to watch the series (lest they're too basic), here:

@Skyler Have you read any of Balarka Sen's posts here?

Imaginary Numbers Are Real [Part 13: Riemann Surfaces]

that question was a bit more tongue in cheek, i am trying to work my way back up

user228700

►

Anyhow I need to work for 15 minutes or so ...

8:07 AM

Riemann surfaces are excellent

8:36 AM

> thus for a system in equilibrium , the value of bulk modulus is always positive.

Which kind of equilibrium?

@JohnRennie do you have some time ?

Yes, what's up?

^what kind of equilibrium?

@Ramanujan I've no idea. Have you got a link to the original statement?

@JohnRennie lacking in physics :(

A positive bulk modulus means that when you compress something the pressure goes up i.e. is resists compression. And when you stop compressing it the increased pressure will make it expand again.

But suppose the bulk modulus was negative. That means when you compressed the object its pressure would go down not up.

And the more you compressed it the more its pressure would go down. So it would just shrink away to nothing.

That's why any system with a negative bulk modulus is unstable.

8:52 AM

@JohnRennie ? Increase in pressure and decrease in volume

The bulk modulus is $$K = -V\frac{dP}{dV}$$

A positive bulk modulus means that if you compress something, i.e. reduce the volume, the pressure goes up.

Which is kind of obvious. If you compress a gas its pressure increases, and if you let go of the gas it expands again.

$\huge{:(}$

2

I have to head off for a bit.Back in an hour or so.

Ok

DanielSank

9:10 AM

I am totally fascinated by how many down-votes this has attracted.

two each on the question and answer.

It's a perfectly harmless post.

I can only assume the same two people exercised the down-arrow here.

I mean, who the hell downvotes submissions in a silly fun thingy on the meta?

9:51 AM

@DanielSank it wouldn't be so bad if people said what they objected to. I suppose people fear retaliatory downvotes.

@DanielSank Those are the exact words the naked physicist used :P

Though I do agree it's weird you got downvoted twice

MartianCactus

10:27 AM

in a concave lens

how is OF = FC?

isnt PF is supposed to be equal to FC?

10:57 AM

$$ \huge{\int )::(}\int$$

@Secret What on Earth are you trying to make?

Oh

I am just super bored and frustrated as I keep making careless mistakes when I try to elucidate the symmetry of some integrals

I assumed you were trying to make some kind of artwork with LaTeX...

well, you can call that some kind of lovecraftian creature, I guess, since it has 4 eyes at the centre

@Secret Also, if you wanted it bigger, ya could've used \Huge instead of \huge :P

11:01 AM

$$\Huge{\int )::( \int}$$

much better

@Secret Also pretty sure \Huge and such don't require curly brackets

Just spaces

hello

welcome food for thought

thanks

r u excited about trump?

nah, I'm not interested in politics

u?

11:13 AM

yeah I'm excited

I love politics though

the science of organising humans to achieve maximal productivity

poli sci

:-)

yeah

hello

hi swapnil

Sup?

11:20 AM

good u

Good.

good

good

Lol

When 40% don't vote, it doesn't mean much to me.

11:32 AM

what doesn't mean much?

why does it matter how many people vote?

just politics, in general

I think the fact 40% don't vote is a reflection that people aren't interested in politics

as opposed to being a reason to not be interested in it

yup

join the crowd

I'm interested in it because it has the potential to have a real impact on people's lives

like the world will be different under Trump than Hiliary

so I'm interested in understanding what the differecnes are

and those who understand their environment (physical, social etc.) will thrive

hi @Kaumudi.H

how r u

I heard trump used Twitter a lot

user228700

11:36 AM

@Ken: Hey :-)

user228700

I'm good, thanks. What about you?

yeah he does

he's very hip

i'm gud 2

just chilin watching the tennis

user228700

How's the website coming?

it's Aus Open season

user228700

@Kenshin Nice.

11:37 AM

na been too busy to do much on the website

but it does have like 120 questions

user228700

Oh, OK. That explains why you haven't been around as much.

user228700

Do u play tennis?

yea

I played for 10 years or so but I don't play much now just for fun on occasion

user228700

Oh, wow, I see. I play badminton sometimes.

oh yeah that's fun too

i was the badmintong school champ

user228700

11:40 AM

Wow. Cool :-)

user228700

Say, how's the climate over there this time of year?

boing atm

boiling

like 30-35 celcius

up to 40 in melbourne some days where the Aus Open is at

but it's ok if I stay inside with the aircon on

user228700

40?!

user228700

Wow.

yeah

yeah on Tuesday the tennis players had to play in that heat

user228700

11:42 AM

We had 42 once but it's usually never that high.

yeah 40 is rare her too

average is about 30 atm with a few 35 days

and like 1 40 day a month in summer time

If stress is directly proportional to strain,then can we say strain is directly proportional to stress?

@Ramanujan yes

y=kx

user228700

@Kenshin That's still a little crazy, wow.

11:44 AM

Then Young's modulus = strain/stress?

x = (1/k)y

Hmm

let j = 1/k

then x = jy

thus if y is proportional to x, x is proportional to y

Also you can think about it as a graph, if y is proportional to x you can draw a straight line on a y vs x graph that passes through 0

if you plot instead x vs y, it will still be a straight line passing through 0

user228700

Oops, @Ken: Bye :-)

tata

user3183950

12:35 PM

.

12:54 PM

Note: k is a nonzero constant. If k=0 there would be "variation."

1:43 PM

[physics.stackexchange.com/questions/306639/…

heather

2:14 PM

hello

2:24 PM

Howdy

ACuriousMind

2:41 PM

> Our solar system has moved in a higher energetic space, and/or the Nemsis system, aka Nibiru/ planet X, causing our Sun tot shine brighter with white light instead of yellow. Note that therefor the Moon and Venus are brighter.

Is there a reason why the esoteric guys love to call the whatever life force or agent in their worldivew "energy", even though it is not really energy as understood in physics?

From some of the low quality PSE questions, they seemed to commonly attribute this to electromagnetic radiation, but EM wave behave nothing like what their worldview defined as "energy"

I always puzzled at what they are thinking. Even in the context of their worldviews, there seemed to be no consistent notion of logic behind how they define things

ACuriousMind

@Secret Because, in everyday language (not just that of esoteric crackpots!), "energy" is a much more vague concept than in physics. Just ask someone with no formal training in physics what the difference between energy and power is.

yeah they just use them interchangeably, and most ordinary people seemed to have this notion that if something has more power, it is stronger, more resilent, (insert bunch of suitable terms)

ACuriousMind

Yes, that's because that's what "power" means in ordinary language. They're not wrong, they are simply not aware that everyday language and technical usage differs.

2:58 PM

Sometimes it gets confusing when your audience is full of people with diverse backgrounds, and then it happens there are some words that most of them use, but mean completely different things to them, resulting in the need to sort of act as a translator to phrase that word n times in the context of their fields