@Blue think itll be big deal when it opens, cant find any info on date. wikipedia doesnt even mention the 50qbit model yet. en.wikipedia.org/wiki/IBM_Quantum_Experience

suppose i have a constant speed so im at rest . so i have mv momentum and after some time im again in constant speed but different from the one in the beginning but im at rest again. that means that the change of momentum mv1-mv2 is not zero although i was atrest and then at rest again ?

or being at rest means only v=0

@ManolisLyviakis momentum is always seen from ground frame (inertial frame/ lab frame)

@ManolisLyviakis you cant measure momentum from car frame.

ohh i get it so v=0 when we say at rest for momentum

Yep.

thanks

the internal forces are not zero in a system of particles right?

although they are equal and opposite

@ManolisLyviakis their vector sum is zero

then why doesnt he say its zero

ooooh i got it i think

@Blue yeah apparently 16 qubits have been available to public for awhile, it would be nice if there were a list of papers/ other refs/ uses etc

the double sums of the internal forces would be zero

At an interview. It starts at 10:30. I am supposed to teach a topic to a panel of computer scientists. I am suited up and well groomed. Have my notes prepped

what happens to momentum in periodic motions?

its zero?

i mean the change of m,omentum at the start and after one period

@ManolisLyviakis Do you think momentum is conserved for small oscillations of a simple pendulum?

(Hint: $\vec{p}= m\vec{ v}$)

i think that there are symmetric

velocities

with opposite signs

But velocity is constantly changing nevertheless.

Which implies momentum is not conserved

Momentum is conserved only when the net external force is zero.

but im am to prove that external energy is zero when there is a periodic motion

prove that the average external force of a system of N particles doing a periodic motion is zero

ina period

in a period of time

@ManolisLyviakis Can you prove this for the SHM of a simple pendulum? It's easy.

Remember that velocity at extremes is 0.

And be careful with the direction of velocity at the mean position.

That's it!

i dont understnad what i have to prove if as you said momentum is not conserved in periodic motion then how are the external forces zero?

proving the external force is zero is proving momentum is conserved

@ManolisLyviakis you are not paying attention to the word "average".

Let the pendulum motion begin with $\vec{v}$ velocity.

i dont have a definition for it

right side is positive and left side negative in our coordinate system

Then:

When the pendulum mass reaches the extreme position,

$\Delta p_1 = m\vec{v}$

When it reaches the other extreme:

Δp ?

$\Delta p_2 = m({-\vec{v}})= -m\vec{v}$

@ManolisLyviakis change in momentum

dont you mean $p_1=mu$

and $Δp=p_2-p_1$

Average force = $(\Delta p_1+\Delta p_2)/\Delta t = 0 $

what is the change of momentum to just one point?

@ManolisLyviakis mass times velocity

isnt that just the momentum?

oops sorry, I meant mass times change in velocity.

@Abcd how's the explanation thing going ?

@JohnRennie ah

I was going to ask exactly how you did that

but I see the nice oneboxer has obliged

does it make sense to be bad at physics and good at math?

@ManolisLyviakis Yes.

Physics isn't math and math isn't physics.

Though physics relies quite heavily on math.

i thought with my knowlegde of math i would totally own classical mechanics

Nobody total owns CM.

ah, @dmckee, you're in

I have a question

How unreasonably complex and difficult that subject is, is the dirty secret of our discipline.

a... friend

i can understant derivation of lagranges equations and all that but im so stuck at formulating random problems

got a referee request from a reasonably high impact journal

I have a question I want to ask on another SE site about ... a friend, too.

@EmilioPisanty Good for your friend.

which may or may not be +1-coded to qsm

for a paper whose second-to-last author is my friend's PhD supervisor

this friend of mine defended their PhD in the fall of 2016, so, about a year and four months ago

@EmilioPisanty I'd say your friend should disclose the above fact to the editor,, but agree to review as long as they think they can be objective enough about the content.

@dmckee interesting

so you don't think it's automatically a no-no from a COI perspective?

Presumably your friend was not directly involved in the work, right? Or they would be an author.

@dmckee and yes, that's what my friend did immediately upon seeing the full author list

And review doesn't have to be pristine—can't be in small fields—it just have to be good enough. So let the editor decide.

@dmckee it's in the same topic as my friend's PhD project but they were not involved in that work at all

@EmilioPisanty That relationship to the topic is why they were asked.

@dmckee maybe they just didn't notice?

@Blue on it now :)

@EmilioPisanty That's why your friend points out the situation. So the editor will definitely know.

As long as the editor is happy, your friend should definitely jump at this opportunity.

my question physics.stackexchange.com/questions/389366/… has been marked as a duplicate, but I've edited my question to point out that I still don't know the answer to my question. Can someone give me the answer to my question here?

It's not everyone who gets asked to review for a moderately important journal.

@dmckee yeah, the email to the editor said that the relationship exists but that it's ultimately up to the journal to make the determination and that they're happy to review if the journal wants it

@dmckee yeah, my friend was pretty happy when they got the initial request

@EmilioPisanty I think that's the best they can do.

@EmilioPisanty I'll bet.

... which had all the authors except the last two

and also, the last author is my friend's PhD examiner

@Blue not much help :(

@dmckee but they should expect some communication from the journal before plowing ahead with the review?

@Blue could you explain it to me ?

@Blue okay.

@EmilioPisanty Time permitting they could ahead and read it for pleasure and practice. That way they can respond promptly if the editor still wants the review.

@dmckee well, that friend is pretty busy but they do like to procrastinate

thanks for the help =)

Congratulate your friend for me. That's a big deal.

@dmckee well, it's their second review for that journal. (and they took absolute ages on the second go-round of the first review because it was on the home run of their thesis. so the invite does imply that that didn't ruin things there.) but yes, it is, and I'll tell them. =)

anyways, gotta run

thanks for the help

hallooo

@Blue Tad slow... been distracted by school now it's back in business (no snow)...

But still carrying on in the background

I was a tad annoyed cause it closed school on a day that I needed to do my coursework but it was a nice 4 day weekend I s'pose

@Blue Sure thing :p

Ooh sounds fun (idk what it is, might not be)

but sleep is good

I seem to have been sleeping on someone's sofa every sunday morning for the last three weeks.

Think this weekend I might get some sleep in.

Well, I do know them...

But like loads of people turning 18 around now

Yup

gotta go willld

Switzerland drinking age non-spirits is 16 iirc

Oh wow, fair.

crazy wild down in Africa

question : A student collected 51.2 ml of $H_2$ over water at 180C (Vapor pressure 15.5mm Hg at a barometric pressure of 736 mm Hg. What fraction of mole of gas is in his sample?

How do I relate all this information ?

why is it a big deal to be able to drink when you're 18

i only care about pushing some morphine down there

@Tanuj 51.2ml is a volume, and it's given temp and pressures

Ideal gas laws?

@CooperCape yea , but there is something else too.

@BalarkaSen I don't think it is particularly, just that everyone can now buy their own when they go out instead of finding it in their parents cupboards...

(For the record, I have never done either)

@CooperCape I doubt vapour pressure = gas pressure

true dat

yeah fai

me no concentrate

@Tanuj I think the student collected some water vapour too.

@Abcd that's what i thought . But then shouldn't aqueous tension also be given ?

@Blue Getting out of school is terrifying.

@Tanuj which chapter is this from? Gaseous state of chemistry?

Freedom for what son

what are you going to do with all that freedom

maybe , also could be from solutions

nothing

@Tanuj Then I don't know :/

if the ability to do that classifies as freedom then so is my ability to sing "I CANT GO BACK TO YOUR PROWLER LAND" at the top of my voice on the middle of the night until i wake my neighbors up

which I can certainly do

you don't know the first thing about freedom dawg

you naive kid

shakes fist

turns into Dostoyevsky

@Tanuj See this: chemed.chem.purdue.edu/genchem/lab/techniques/gascollect.html

@Tanuj what does that mean?

why did you want it deleted ?

@Blue What does it mean?

@Blue Ah, okay.

@Tanuj Because you're revealing someone's private information without the person's consent?

Exactly!

Private info ? Lol he is definetly not the only one in the world with that name. Also , it was just a name , not even a full name.

But I still deleted it you see.

Also, tad odd.

I didn't know someone's name would be a 'private information'

If someone @'d me with "Jordan?" I'd be like woah.

@Tanuj Even I wouldn't be OK if someone posted my first name here!!

@Abcd why ?

@Tanuj An anonymous user's real name is private information if they do not want to reveal it, yes.

This is my first name btw , Tanuj :)

@Tanuj If you are okay with it doesn't mean everyone is :). Everyone has a different sense of privacy.

How would I know if he didn't want to reveal it.

Well now you know because he told you to delete it

yea , forget about it .

@Tanuj Did that site help?

@Blue could you have a look at it ?

A student collected 51.2 ml of H2 over water at 180C (Vapor pressure 15.5mm Hg at a barometric pressure of 736 mm Hg. What fraction of mole of gas is in his sample?

@Blue I get it , just don't know how to make sense of this "51.2 ml of H2 over water at 180C (Vapor pressure 15.5mm Hg at a barometric pressure of 736 mm Hg. "

ah okay

@Blue why would I need it ?

@Blue its the vapour pressure of pure water ?

@Tanuj there was some law for those types of problems...

Ah, Blue mentioned it. Raoult's Law, yeah.

@Sid lol really ? I thought it was hit and trial that was to be used.jk

@Tanuj When is JEE Main?

april 8

I just gave a mock and got a mere 149

@Tanuj Done with full syllabus?

nope .

Are you leaving any chapters?

yup .

idek ,

whatever I can't complete will be left automatically

@Sid did you give mocks last year ?

@Tanuj I guess. Gave some 10 or so Mock papers

@Sid how much did you score on average ?

@Tanuj Are you a dropper?

Don't remember. But, my score on Mocks and Mains was not very different.

yup

Anyway, I am not a huge fan of JEE anyway. They fail to imbibe a very important virtue in students or rather put students away from that

which virtue @Sid ?

Use of Calculators. It's appalling to see how much time my colleagues waste doing tedious sums because they have been trained to do so during their prep years

And more often than not, this leads to many errors

Thats not a very important virtue...is it?

Heh.

JEE has more serious issues than not teaching students to do without-calculator computations lmao

More important than you would think.

@BalarkaSen yeah!

@BalarkaSen well, yes. But, I don't know a better way to evaluate a million students. But, that specific part is a glaring error

I mean you can think of the importance of off-calculator computations as nested inside the issue of enhancing logical thinking capabilities

Which is a larger and fairer context

@BalarkaSen perhaps true. But, it does make students very one-dimensional. Especially when people are willing to do mechanical work even if they have a machine that does the same infinitely faster for them

Well I cannot come up with an instance where hands-on computations of some certain tedious multiplication say (which is really one of the most time consuming operations in elementary school: the usual schoolbook procedure runs on time complexity O(n^2)) is more useful to do by hand than plugging into your calculator, except to have an active control on the computational part of your brain

That's just an example by the way

Bonus meme: What's the fastest (in terms of complexity, as a function of # of digits) algorithm for multiplication we know so far?

Got the job👍👍👍👍🎉🎉🎉😺

At the beach for a swim.

Jumpin' Jeebus on a pogo stick! What good is a would-be philosopher who can't distinguish between a phenomena and some observable related to the phenomena?

The phenomenon is perceptible by the senses but is not the perception!

Postmodernist neoMarxism conflates perception and the perceptible

praise the Marx

Please, Marxism-Leninism differentiates the two well :p

That was a big foundation of the dialectal materialism as applied to sciences!

But unfortunately post modernism etc

postmodern neomarxism \neq marxism leninism

ok maybe praising marx was too far

praise the derrida

Fortunately the post-modernists are too invested in trying to solve how white supremacy affects science to try their meaty hands at it

Ah. And now someone else who wants a "proof". Mathematicians do proofs. Physicists do experiments and derivations. And you youn'un's need to get off my lawn!

Physicists do proofs, they just do them badly

Well for physicists the notion of proofs is different from the mathematician's notion

Hm

Is a cylinder isometric to the same cylinder with a Dehn twist?

Well, in my nomenclature the main difference between a derivation and a proof is that the former starts "Assuming that [theory] describes [phenomena] ..." , and the latter starts from axioms that simply are true in the context of the proof.

So it is a distinction mostly of mindset. But I find that students who consistently use the word "proof" are more likely to overlook the fundamentally descriptive nature of science.

Oh there's a lot of physics like the latter, too

Apparently this is the famous 95 Witten talk, or done just around that time

math.stonybrook.edu/Videos/IMS/video.php?f=35-Witten

"So I propose"

Is anyone here experienced in antenna theory and practice?

I have an antenna

On my head

to communicate with my alien overlords

@Slereah Are you Andorian

Watch yourself, pinkskin!

I just discovered that NOAA weather satellites have a public downlink for anyone to decode

Like

Anyone can tune to the downlink frequency and extract LIVE images

Of course I need to try this but I don't know jack shit about the EE in antennas

@HsMjstyMstdn Nope, but it does sound awesome

Hollywood has its moments.

@BalarkaSen Incredibly accurate sadly

Kubrick did make great trailers

@dmckee lol what are you talking about?

Kubrick is OK

I still have to watch that one Soviet/Russian film you told me about @Balarka. I'm sure I have it saved somewhere.

Watch it damnit

I know, I should. I don't enjoy movies for the most part. Waiting for the moment when things fall in place and there's some probability of me finally watching one.

Sometime soon. Though I think I said that the last time as well haha

It's ok :)

Also, I need a good screen with nice speakers. Not a puny laptop

Let me know what you think of it afterwards and I'm happy :)

@BalarkaSen OK? That trailer I posted is a work of art :P

Home now

Going to rest and then do some QED, then some mathy things

Still prepping to push out the Klein-Nishina derivation hang tight people. It's comming