The h Bar

12:14 AM

@0celo7 Yeah, I know Spanier. And I've written exams that went like that. Better to do it on the first exam than on the final.

dmckee

@whatin1992 Because the stationary states of the system are eigenstates of the operator $\hat{\mathbf{L}} = \hat{\mathbf{r}} \times \hat{\mathbf{p}}$ even though they are not eigenstates of $\hat{\mathbf{r}}$ or $\hat{\mathbf{p}}$.

That's quantum mechanics for you. You care about eigenstates and eigenvalues, not classical pictures.

rob

@0celo7 As a matter of fact ... I took that sophomore Modern Physics class from Bill Bugg, who was the department head for a long time and had pushed to have the SSC sited in Tennessee rather than in Texas. And I remember that most of the class failed Bugg's first exam, too.

At the time, he warned us: "I always make the first exam too hard, the second too easy, and I get the level about right for the final." We thought he was joking, but that was what happened.

Bernardo Meurer

@0celo7 You around?

Physics Meta

12:32 AM

-1

Q: When should I write a symbol in italic type, when upright?

I sometimes get confused with scientific notation. Sometimes things are in italic font, sometimes in upright font. Is it $e$ or $\mathrm{e}$? Is it $dx$ or $\mathrm{d}x$?

discussion

0celo7

@BernardoMeurer For a minute, yes

about to leave again

Bernardo Meurer

Migos - Bad and Boujee but it's only Lil Uzi Vert saying YAH YAH YAH the whole song

►

@0celo7 That

0celo7

I watched it already

Bernardo Meurer

SID THE SCIENCE KID-BAD AND BOUJEE (OFFICIAL VIDEO)

►

This one too?

0celo7

lol

dmckee

12:53 AM

Looking at SMBC physicist jokes again. For reasons.

Found ...

smbc-comics.com/comic/a-severe-disorder

2

again.

Reminded that I want someone to give me trebuchets when I'm fussy, too.

NeuroFuzzy

Ocelot's back!!!!

Bernardo Meurer

@NeuroFuzzy @DavidZ Latest Xwayland patch fixed the issue with non-clickable windows I had reported

0celo7

1:19 AM

@NeuroFuzzy maybe not for long

ACM is pretty mad at me

@BernardoMeurer can you pls help me with that

Bernardo Meurer

@0celo7 Hm?

0celo7

I said you were autistic to protect you from the invading mods. ACM thought it was an inappropriate joke. But little does he know that I was telling the truth...

It's not an insult if it's the truth

Bernardo Meurer

I could be autistic, I'm non-offended

DanielSank

@BernardoMeurer <3

@0celo7 <3?

Bernardo Meurer

@DanielSank <3

skill patrol

1:33 AM

</3

0celo7

@DanielSank <3

Why the question mark?

DanielSank

@0celo7 Wasn't sure if you'd receive my <3 well.

0celo7

@DanielSank I enjoy talking to you, so I did receive it well

skullpetrol

</3

DanielSank

@skullpetrol <3

skullpetrol

1:39 AM

:D

skill patrol

@DanielSank <3

DanielSank

Oh man, skullpetrol and skill patrol. I can't handle this.

@skillpatrol <3

ACuriousMind

@DanielSank You don't need to, they're the same person.

DanielSank

@ACuriousMind True or false?

Hmmm, they do both like the Raiders.

ACuriousMind

Aug 2 '15 at 12:49, by skill patrol

Nah, skull is my mobile username...

DanielSank

1:44 AM

But... why?

Do I need a mobile username?

ACuriousMind

Beats me :P

DanielSank

Am I {doing it wrong}?

0celo7

@ACuriousMind can you forgive me

5

skill patrol

::crickets::

skullpetrol

over 9,000 hours later...

David Z

3:19 AM

@DanielSank Well you could just have a non-mobile username but if you get up and move you become anonymous. Probably better to have one you can take with you. :-P

skill patrol

4:14 AM

@DanielSank^

obe

4:40 AM

hey

Sir Cumference

5:03 AM

Howdy

skill patrol

5:22 AM

hi

Physics Meta

5:44 AM

0

Q: Broken internal link

I just came across this post, whose first link is to here, which is actually broken and goes to a totally wrong post on a wrong site. I noticed that the Linked section on the right contains the correct link to this post. I guess what happened is that the link in the question pointed to the origin...

discussion bug hyperlinks

DanielSank

6:00 AM

@DavidZ Hmmm.

Perhaps.

2

user228700

7:47 AM

Hi, everyone :-)

skill patrol

2 hours ago, by skill patrol

hi

:-)

user228700

:-)

user228700

@JohnR: Are u busy at the moment?

John Rennie

No, I'm ina pause between bits of work so now I'm just drinking coffee and listening to the radio :-)

user228700

OK :-) Carry on, then. I think I've solved the problem...

John Rennie

7:51 AM

You have about 45 minutes to ask about physics, bicycles, diet or indeed anything else not related to electrodynamics :-)

3

@Kaumudi.H aha. As it happens I'm just out of coffee so I shall make it a priority to brew some more.

user228700

OK :-)

Slereah

why can't i find a place that has the Haag construction of scalar field theory in details but without unrolling the whole history of QFT

user228700

@JohnR: Alright, it turns out that I have not solved the problem.

Slereah

I don't want to read 200 pages of Haag's book to learn that

John Rennie

@Kaumudi.H OK?

user228700

8:01 AM

Sigh. A website is asking me to upload a photograph with specific (pixel) dimensions. However, I'm not allowed to crop my photograph (passport-sized) and they also need the photo to be of size 15-30 KB and I dunno how to satisfy all these criteria.

Slereah

Reduce size and crop, then if too big, reduce quality until it fits

user228700

Reduce size?

Slereah

Reduce the size so that your face is proportional to the size required

user228700

Exactly what dyou mean by "reduce size"?

Slereah

Resize the photo

John Rennie

8:05 AM

@Kaumudi.H when you save a photo as jpeg you can specify the amount of compression.

user228700

OK..?

John Rennie

The greater the compression the smaller the file size.

DanielSank

@Kenshin I removed the link to your gravity answer from the "Best of" meta post.

Please do not re-add it. I do not want to get into an editing war.

John Rennie

So start by resizing the photo to the required number of pixels, then save it at low compression/high quality. If that is too big save it again with a higher compression/lower quality.

user228700

Gimme a minute, please...

John Rennie

8:06 AM

Repeat until the size is below 30KB.

user228700

What? The current size is only 5 KB, I don't need to reduce the size. I've been adding long paragraphs to its description, title, etc. to increase its size...

DanielSank

Hi, everybody.

@heather How to fill the gap between classical physics and quantum physics

2

John Rennie

@Kaumudi.H save it at higher quality then. If you would like to mail me the picture I can have a look.

@DanielSank I posted a link to a blatant duplicate, and still people post answers.

DanielSank

@JohnRennie You can only do what you can do.

user228700

I've just found out that more work needs to be done (on the photo) before I can upload it (add date, name, etc.) Please gimme a minute...

DanielSank

8:13 AM

The question text is incredible. How to fill the gap... yes good question indeed.

John Rennie

@Kaumudi.H Add date and name to the photo? You mean save it as metadata in the photo?

user228700

@JohnRennie No, add it on the photo.

John Rennie

OK, but that will make little if any difference to the size of the file.

If anything it will reduce the file size

user228700

I know, but the website requires me to do this...

John Rennie

Have you got a master copy of the photo at high resolution/large file size?

user228700

8:17 AM

No, I'm afraid not. I scanned a hard-copy and then cropped it to remove date, name, etc. to upload to other websites. Now I'm working with this copy. I've just added my name and date again.

user228700

Dyou know how to resize a photo in terms of pixels?

user228700

I've tried many websites but most of them crop the picture. Is that the expected result?

Dipesh Bhandari

I'm sorry . I'm new here. Do I just barge in this conversation or something ? What do I do to ask questions ?

John Rennie

@DipeshBhandari just ask. We routinely have many parallel conversations going on.

@Kaumudi.H I would resize using some image software e.g. Paint Shop Pro. Windows paint might be able to resize images.

user228700

One second...

John Rennie

8:25 AM

Yes, I've just checked and the Paint app in Windows 7 can resize images.

Dipesh Bhandari

@JohnRennie oh okay...thanks

John Rennie

@DipeshBhandari what did you want to ask?

Dipesh Bhandari

@JohnRennie Some problems from the previous olympiads. This is the place to do that right ?

DanielSank

@DipeshBhandari Generally, add a question mark to the end of an interrogative sentence :-)

@DipeshBhandari The main site is the best place for Q&A. If you have something requiring discussion unfit for the main site, then bring it here.

user228700

@JohnRennie Not well, I'm afraid. It simply crops the picture.

user228700

8:28 AM

No matter though--I've managed to find a website that does this job quite efficiently. I'm trying to upload the photo now (After having added some gibberish to the description of the photo to increase its size)

John Rennie

@Kaumudi.H Shall I mail you a link to the image software I use?

@DipeshBhandari yes, you can ask in the chat.

Dipesh Bhandari

@DanielSank Yeah thanks..but the main page would take some time. Here I can talk to the pros of Problem Solving I think.. :-D

user228700

@JohnRennie This is the website that I found: picresize.com

John Rennie

If you just post Olympiad questions on the main site they are likely to be closed as homework.

DanielSank

@DipeshBhandari Warning: Saying that you want to save time, while expecting the "pros" to spend time, is a recipe for making people not want to help you.

In any case, ask your question and let's see if it's good for chat or should be on the main site

user228700

8:31 AM

@JohnR: Yes, I've managed to upload it successfully! Thank you! :-)

DanielSank

@Kaumudi.H d00d, just use Inkscape or something.

Oh, never mind.

John Rennie

@DanielSank for bitmaps?

DanielSank

@JohnRennie Sure.

If the goal is to reduce size, you can just export as a low res bitmap.

Dipesh Bhandari

@DanielSank okay...thanks

DanielSank

@DipeshBhandari So what's the question?

user228700

8:34 AM

x'D I've been adding the last "letter" from "The Perks of Being a Wallflower" to the description of these images to increase their size.

DanielSank

@Kaumudi.H wat?

user228700

@DanielSank ^

user228700

It used to be 4 KB, now it's 18 x'D

DanielSank

Why make it bigger?

user228700

8:37 AM

'Cause website requirements.

DanielSank

ah

Oh, I've been meaning to ask you, how is your question of reducing the world suck going?

3

Has there been any recent reduction?

user228700

It's an ongoing process; I find that I am able to reduce some everyday :-) I contributed some more when I added subtitles to some YouTube videos the other day.

DanielSank

@Kaumudi.H Very good!

user228700

What about urself?

DanielSank

I have not reduced much suck recently. However, I have added awesome to my own life.

Awww, dangit. There's a typo in a message that just got starred and I can't fix it.

@JohnRennie do you have chat magic?

Anyway... @Kaumudi.H I made ma'amoul cookies. They are delicious.

John Rennie

8:42 AM

Sadly room owners don't have that particular superpower. You need a friendly moderator.

DanielSank

dangit

user228700

Nice! :-) Did u give said delicious cookies to other people? U have reduced some world suck, then!

DanielSank

Hmmm, isn't that true only if they were having a bad day?

Otherwise, is it not an addition of awesome rather than a reduction of suck?

@ACuriousMind when you get a chance, plz edit "question" -> "quest" here:

5 mins ago, by DanielSank

Oh, I've been meaning to ask you, how is your question of reducing the world suck going?

user228700

I don't think so. If they enjoyed the cookies, then u added some awesome, which they may have carried with themselves to go on and reduce some world suck.

DanielSank

Ohhhhhhhh! Now I am understanding the physics of world suck and awesome.

Thank you!

user228700

8:44 AM

Lol x'D U're welcome (?)

DanielSank

So then... I should produce more cookies.

user228700

Definitely!

DanielSank

I see. Very well, then.

I have another box of dates and plenty of farina. I can make more cookies easily.

user228700

:-) All the more reason to make more of them delicious cookies!

DanielSank

Have you tasted ma'amoul?

user228700

8:45 AM

Nope :-(

DanielSank

But as I recall dates are too sweet for you, right?

user228700

Yes, I don't like to eat them on their own.

user228700

Ugh, this website!

DanielSank

I see. These cookies use a coarse wheat flour. The dough is pressed into a special mold, as you can see here:

thefooddoctor.files.wordpress.com/2013/08/…

user228700

Pretty! :-)

DanielSank

8:48 AM

Then, we add a lump of date paste. The paste includes also orange blossom water for flavor, and of course cardamom and nutmeg.

Then the dough is folded over the lump to form a filled cookie.

user228700

Ooh, I have not tasted cookies with these many flavours!

DanielSank

For me, these are special cookies.

one moment...

user228700

I have to dash out for a few minutes to fill an application form...

DanielSank

user228700

9:07 AM

@DanielSank Again, they look pretty :-)

skill patrol

Howdy @SirCumference

John Rennie

@Kaumudi.H university application?

user228700

Yep!

user228700

Entrance exam, to be more precise.

John Rennie

@Kaumudi.H scary!

DanielSank

9:16 AM

@skillpatrol What about it?

John Rennie

It all starts feeling real!

user228700

:-( Indeed, it is. It's scarier to me, given the horrors that I have already experienced last year.

user228700

> "Your session has been timed out"

user228700

I did not know that this was a possibility, please tell me in advance if u are going to do this aaah!!!

John Rennie

@Kaumudi.H I'll get that inscribed on my gravestone

2

user228700

9:18 AM

x'D That's brilliant!

user228700

I only have about 6-7 weeks before the madness starts...all over again.

DanielSank

@JohnRennie That's brilliant.

John Rennie

@Kaumudi.H On the flip side in 8-9 weeks normal life can resume :-)

user228700

@JohnRennie Nope. 15-16.

John Rennie

Wow, the exams go on for two months?

user228700

9:22 AM

Yep.

user228700

April and May.

DanielSank

I'm confused about Kirchoff's laws.

Does current flow through capacitors or not?

How do I not know this?!

John Rennie

Charge can flow on and off capacitors, though not through them.

DanielSank

@JohnRennie Right but that means there is current flowing through the cap.

John Rennie

So if you are only considering DC current cannot flow through a capacitor. But in an AC circuit current can in effect flow through a capacitor.

DanielSank

9:29 AM

----c----
| |   | |
L c   c L
| |   | |
---------

That's the circuit.

Two LC oscillators connected through a capacitor.

user228700

9:45 AM

Two hours it's taken me to apply. Sigh, I wish the system would be more efficient and accessible.

user228700

And now, I've gots to print out the application form and send it via post! Why?!

DanielSank

Because bureaucrisy.

Yashas Samaga

@Kaumudi.H which college have you applied for?

user228700

Uh, hello there, stranger.

Yashas Samaga

I was just curious to know which college asks you to apply online and then send a hard copy of the application.

user228700

9:51 AM

KEAM (cee-kerala.org/index.php/keam)

Yashas Samaga

not surprising

user228700

Why not?

Kenshin

@DanielSank why did you remove it?

there are other answers with net negative downvotes

Yashas Samaga

government exam :P

Kenshin

so why did you single out my answer as not worthy of the award?

user228700

9:54 AM

@YashasSamaga State govt., yes...

Kenshin

if you cannot justify this then I see no reason to edit the post with the correct details

Yashas Samaga

I had to submit the exam fee for Karnataka CET through a DD when I wrote it.

the application form was annoying

user228700

Oh, I see. Yep, this website is terrible. It's taken me two hours to complete the procedure.

Yashas Samaga

There was all sorts of nonsense in the application form. I had to google countless words to understand what they meant.

Ultimately, I wasted 2 days and never took the test :D

user228700

Lol :-P If u don't mind me asking, are u a dropper as well?

Yashas Samaga

9:57 AM

aw

I did not take the CET test because it would waste two days before the JEE Advanced test

user228700

Hmm?

Yashas Samaga

I had already secured admissions at IISc before that

so I had no worries

user228700

Oh, nice! Through KVPY?

Yashas Samaga

yes

user228700

Awesome! So dyou study there?

Yashas Samaga

9:58 AM

I dropped out :D

sounds insane

I understand that

user228700

Out of IISc?!

Yashas Samaga

don't ask lol

user228700

:-P OK. So are u not in college at the moment?

Yashas Samaga

yea

user228700

Oh, OK. Are u writing JEE again?

Yashas Samaga

9:59 AM

ye

user228700

Cool. Best of luck :-)

Yashas Samaga

Thanks. Best of luck for you too.

Qmechanic

1

Q: Transfer function analisis

I've seen this problem solved out there but I don't quite understand what it is done Based on the transfer function $$ P(s)=\frac{(s+2)}{(s+0.5)(s+4)} $$ it is asked to graphically evaluate the unit step response. I understand the poles and zeros are like in the picture. The step pole is in ...

homework-and-exercises linear-systems

Migrate to Signal Processing?

user228700

Bye, everyone :-)

Emilio Pisanty

Hey @Qmechanic, I'd be grateful if someone took a look at this one. If I reply to the comment (third in a row) I'm liable to lose my cool.

John Rennie

10:14 AM

@Kaumudi.H Bye

Emilio Pisanty

@Qmechanic if DSP would find it on-topic, then maybe. I think it's OK here (if not amazingly on topic), particularly since it did find an answer.

It's probably best to leave it alone as it is, at this point.

Yashas Samaga

E = c x B or E = B x c?

which one is correct? I tend to keep forgetting silly things.

Qmechanic

@EmilioPisanty : Removed comment.

Emilio Pisanty

@Qmechanic I'm not sure it'll help that much at this stage.

that's the third time pretty much the exact same comment gets posted

I'm troubled by the insistent comments that classical EM is bullshit without even any semblance of evidence or reference.

John Rennie

@EmilioPisanty Next time flag for moderator attention and request that JD be warned from commenting again.

Emilio Pisanty

10:27 AM

And I'm troubled by the persistence. I wouldn't go as far as calling it harassment, but it's not that far, either.

skill patrol

@DanielSank that is a proper raiders fan reply to

9 hours ago, by DanielSank

@skillpatrol <3

;-)

help

Hiii

Yashas Samaga

hi

help

I have a question , does we can apply torque equation about any point of body

Emilio Pisanty

@Qmechanic @Qmechanic Yeah, that comment is right on the ticket. Thanks.

Yashas Samaga

10:32 AM

@help Yes.

John Rennie

@help You can take moments about any point and the result will tell you the net torque about that point. This may or may not be a useful thing to do.

Yashas Samaga

But you should use torque about the axis of rotation to make solving the problem easier.

help

@YashasSamaga why axis of rotation

When a body is moving then also we can apply at any point @JohnRennie

Yashas Samaga

You are going to measure the angular velocity, angular acceleration, etc. with the axis of rotation as the reference, right?

David Z

@JohnRennie well, flag for mod attention, yes, but I'd be a little wary of requesting. Like, I would not want to see a flag that says "please tell this user not to post so many comments" (not that that's the issue here, just as an example). We get such flags from new users, particularly, who ask for something to be done which seems entirely inappropriate, and with no indication of why they want that thing to be done.

I would want the flag to say "this and other comments seem unnecessary" or something like that, for example.

help

10:35 AM

@YashasSamaga can we not measure it from other points

Yashas Samaga

You can but why do it? You will end up converting it back to the reference frame w.r.t which you are measuring the angular velocity, angular accleration, etc.

Take a problem and try to solve then analyse what would have happened if you had calculated the torque about a different point.

0

Q: Is there any hope of inventing a mirror that can slow photons down?

Always interested in science, I’ve been fascinated by the consequences of the speed of light, and how the passage of time is relative to the speed of the observer. Imagine the effects if we could invent a mirror that slowed down the speed of light reflecting in it! In other words, could we inven...