The h Bar

Phase

2:06 PM

hm

moving messages to a bin room?

Is there a way to 'jump into the trashcan' and read some?

0ßelö7

2:27 PM

@ACuriousMind in the subscription instructions, I don't understand the difference between the general sub and physics

Anonymous

2:38 PM

@SirCumference $\frac{d^2}{(dx)^2}$ would have been better as it looks like a composition of operators. I guess $dx^2$ is just a shorter notation for that. Doesn't matter much anyway. :P

0ßelö7

@ACuriousMind why is there a difference between the two mathematical physicses

Anonymous

physicses ? :-)

Emilio Pisanty

guys, anyone around that's handy with special functions?

CooperCape

When you have a metric the line element is equal to $ds^2$. Is this the change in arclength at a point in a line or what...?

John Rennie

@Phase there is a trash room here that everyone can read. I believe there is also trash room that only mods can read.

Phase

2:45 PM

For the really bad messages?

0ßelö7

@CooperCape it's nothing

Don't worry about it. The metric is a formal object

John Rennie

@CooperCape it's the norm (squared) of the fourvector $(dx^0, dx^1, dx^2, dx^3)$

0ßelö7

@JohnRennie please don't confuse the boy

Emilio Pisanty

also, use roman-case $d$s

CooperCape

ohh boy this hurts ma brain....

Phase

2:46 PM

This is sad

It's like

where shitty meme conversations go to die

John Rennie

@CooperCape it's simpler than you think.

CooperCape

But what I don't understand is where any of the information about curvature comes from in a metric...

Phase

Isn't ds^2 just the square of the differential you get from multiplying through the metric?

John Rennie

If you start at some point and move by a vector $(dt, dx, dy, dz)$ then the metric calculates how far you moved.

0ßelö7

@CooperCape somehow physicists think that this is intuitive. It took Gauss decades to dream it up

It's called the "theorema egregium" (modulo spelling)

ACuriousMind

2:48 PM

@Phase $\mathrm{d} s^2$ is not the square of anything, it's just a notation.

Phase

Oh really? Shieeet

CooperCape

So you use the metric to calculate an arclength right?

0ßelö7

Yes

John Rennie

Yes

Yes^3

ACuriousMind

In "proper" differential notation, it's $\mathrm{d}s^2 = g_{\mu\nu}\mathrm{d}x^\mu \otimes \mathrm{d}x^\nu$, which is not a square of a 1-form unless $g_{\mu\nu}$ factorizes into $g_{\mu\nu} = v_\mu v_\nu$

0ßelö7

2:50 PM

Not in Lorentizan manifolds though

@ACuriousMind but it is the contraction of a tensor with itself. Any symmetric matrix has a square root

John Rennie

@CooperCape: suppose you're walking on a hill ...

CooperCape

right...

John Rennie

We look down from above, so we see just your position projected on the flat ground, and we measure your position as $(x,y)$. With me so far?

CooperCape

yup

John Rennie

Now from my eagle eye vantage point I see you move by $(dx, dy)$.

If the ground you were moving on was flat then your milometer would measure a distance $ds^2 = dx^2 + dy^2$. Yes?

CooperCape

2:53 PM

Uh huh...

John Rennie

But if the ground isn't flat then the distance you move is different to $dx^2 + dy^2$ because you're moving vertically as well as horizontally.

So for me to calculate what distance you measure on your milometer when you move I can't just use $ds^2 = dx^2 + dy^2$. I have to use some more complicated function $ds^2 = f(dx, dy)$.

CooperCape

which is given by the metric?

Anonymous

If the ground wasn't flat, the direction of movement could not be represented by $(dx,dy)$ in the first place, isn't it?

John Rennie

I'm looking from above remember. I can't see vertical motion.

Anonymous

Oh. I see. Alright :)

John Rennie

2:56 PM

All I can see is the motion in the $x$ and $y$ directions.

So the function $ds^2 = f(dx, dy)$ tells me how the hill slopes.

CooperCape

yeah

John Rennie

You must have seen the rubber sheet pictures to represent spacetime curvature. Yes?

CooperCape

yeah

John Rennie

Well in those pictures the vertical dimension is like the $z$ axis in the example of a hill that I just used. But it's important to understand that this extra dimension doesn't exist.

It's just a convenient metaphor for representing the curvature.

CooperCape

yeah okay...

John Rennie

2:59 PM

I think I attempted to explain this in an answer a while back. Let me search ...

Try this:

5

A: Universe being flat and why we can't see or access the space "behind" our universe plane?

When you're talking about curvature it's important to distinguish between intrinsic and extrinsic curvature. I struggled to find a good summary of the difference: page 6 of this PDF discusses it, or Google for similar articles. A very common analogy for spacetime curvature is the rubber sheet, a...

CooperCape

okay thanks :)

Anonymous

One more question: How are we sure that $ds^2$ would be a function of only $dx$ and $dy$. $dz$ could be independent of $dx,dy$. I suppose it should be $ds^2=f(dx,dy,dz)$ (?)

John Rennie

No, no, no, no, no!

Anonymous

Uh?

John Rennie

I'm using the $z$ dimension purely figuratively to illustrate the curvature.

In the example I used the motion is purely 2D. The vertical dimension is just a way of embedding the 2D manifold to make it easy for us to see what's going on.

CooperCape

3:03 PM

so to get an arc length you integrate the square root of the metric?

John Rennie

@CooperCape Yes

CooperCape

so like $$\int_a^b \sqrt{ds^2}$$

Anonymous

@JohnRennie You mean the curvature would be a function of $x,y$ only? And hence we can write it as $ds^2=f(dx,dy)$ ?

John Rennie

@CooperCape in fact look at this question where I do exactly this to describe accelerated motion in flat spacetime:

48

Q: What is time dilation really?

Please will someone explain what time dilation really is and how it occurs. There are lots of questions and answers going into how to calculate time dilation, but none that give an intuitive feel for how it happens.

@Blue yes, because I started out saying we were dealing with motion in 2D.

CooperCape

Holy cow you really went ham on that one...

John Rennie

3:05 PM

@CooperCape I got fed up with people talking bollocks about the twin paradox and decided to write the definitive QAs on the subject!

Anonymous

@JohnRennie Right, right. It does make sense. Thanks

CooperCape

ohhh boy not the twin paradox

John Rennie

50

Q: What is the proper way to explain the twin paradox?

The paradox in the twin paradox is that the situation appears symmetrical so each twin should think the other has aged less, which is of course impossible. There are a thousand explanations out there for why this doesn't happen, but they all end up saying something vague like it's because one tw...

special-relativity time reference-frames relativity

CooperCape

Did you... give yourself a bounty?

John Rennie

My contribution to making the world of physics a better place :-)

CooperCape

3:07 PM

Ahhh fair

John Rennie

@CooperCape :-) no, someone else bountied the question.

CooperCape

oh right... that would seem pretty... pointless otherwise..

John Rennie

But, by understanding what the metric does and how it works you're at least halfway to understanding GR!!!

0ßelö7

@ACuriousMind I really can't figure this email thing out

do I have to send different emails for math and physics?

@JohnRennie eyebrow raise

John Rennie

@0ßelö7 :-) Understanding the basic idea of how GR works.

CooperCape

3:12 PM

Honestly @JohnRennie The Shape of Inner Space has confused me so much taught me a lot and at the same time I swear it's the best book I've ever read....

Yeah I think I'll leave understanding GR to those with/doing a physics degree...

John Rennie

@CooperCape ah, I'm glad you enjoyed it. It's a well written book isn't it?

If you like that sort of book and you've ever wondered what the Riemann hypothesis actually means then I strongly recommend Prime Obsession by John Derbyshire.

It's another book that is quite hard work but will leave you actually understanding what is going on.

CooperCape

Yeah it is... Humorous in some parts where it explains the quadratic formula next to some crazy topology stuffs

I'll definitely check it out...

All I know about it currently is that it's got £££ on its solution

Secret

5

A: Universe being flat and why we can't see or access the space "behind" our universe plane?

When you're talking about curvature it's important to distinguish between intrinsic and extrinsic curvature. I struggled to find a good summary of the difference: page 6 of this PDF discusses it, or Google for similar articles. A very common analogy for spacetime curvature is the rubber sheet, a...

New upgrade to rubber sheet model:

Picture a digital rubber sheet with a grid of numbers counting up one tick at a time.

Now stretch it, the grid deforms. At the same time, the deformed region has slower counting

the why the counting is slowed curved in a continous way consistent to how the grid is distorted, thus it visualise the curvature along the time coordinate as well the space coordinate

Now the question is how to represent wormholes in such framework without self intersection, as a past user had pointed out

John Rennie

3:34 PM

@lyk: hi.

Actually I've just realised you need a minimum rep of 20 to chat here.

Anonymous

@JohnRennie The windows 10 start button(start menu) stops working all of a sudden. I need to restart the computer to again make it work. This is really strange. I searched on google and found that several people faced the same problem with the W10 update. Any way to fix this?

John Rennie

@Blue That's odd. I've got lots of W10 machines and have never seen the problem. If you press the Windows key on the keyboard does that open the menu?

Anonymous

@JohnRennie Nope. Even with the key it doesn't open. I need to restart to make it work. :/

Anonymous

thewindowsclub.com/start-menu-does-not-open-windows-10

Anonymous

Here ^ they claim to provide a solution to the problem...but I'm not sure if I should follow the steps

John Rennie

3:43 PM

Now is a good time to try it before you've put lots of time and effort into configuring Windows.

CooperCape

@Blue I had that with my laptop but no buttons would work on my toolbar whatsoever...

John Rennie

In any case I've found an SSD for you so when you get it you'll be reinstalling Windows anyway.

Anonymous

@JohnRennie Alright...I'll try it at night then!

Anonymous

@JohnRennie wow...you're back home?

John Rennie

No, I haven't left yet. But I'm afraid I won't have time to package up the disk and send it before I go.

Anonymous

3:46 PM

@JohnRennie It's okay...no need to hurry :)

John Rennie

3:59 PM

@Blue I think the Start button/menu is handled by the process explorer.exe so it may mean Explorer has hung.

@CooperCape: please don't answer homework questions!

CooperCape

He'd done all the working :/ oops

just delete the answer then

pretend this neevr happened.

Anonymous

Anonymous

Explorer seems to be working!

John Rennie

Hmm, did you right click the task bar to open Task Manager?

Anonymous

Ctrl+Alt+Delete

Anonymous

4:03 PM

Then clicked on Task Manager

John Rennie

Ah OK. When the start button has hung, does right clicking on the task bar do anything? I ask because Explorer handles the task bar as well.

You could try using Task Manager to kill explorer.exe and see if that fixes the problem. Explorer will automatically restart after you kill it.

Anonymous

@JohnRennie Yes. It does a show a menu. From there also I can open Task Manager

Anonymous

@JohnRennie Trying!

John Rennie

So it's just the start button. That's weird.

Anonymous

Alright....I ended Explorer....now the taskbar has vanished...lol

Anonymous

4:07 PM

The botton part of my screen is empty (black)

John Rennie

Let me try ...

Ah, it doesn't look as if Explorer auto-restarts in Win10.

DanielSank

@JohnRennie is there some nonsense wherein a presumably pdf document is secretly a docx?

John Rennie

@Blue In Task Manager click File/New Task and type explorer. That will restart Explorer.

@DanielSank not that I'm aware of ...

DOCX is XML and there may be tags to embed a PDF.

Anonymous

@JohnRennie Done! The start button is now working again

Anonymous

strange

Anonymous

4:11 PM

Only the Start menu process gets hanged...not the taskbar as a whole

Anonymous

Currently it is working though

John Rennie

If restarting explorer.exe fixed it then it means some part of Explorer is hanging. Explorer is a multi-threaded app and presumably the thread that is handling the start button hangs.

Anonymous

@JohnRennie Yup...

John Rennie

At least you know how to fix it without having to reboot, though continually having to kill and restart Explorer is rapidly going to be a pain.

Anonymous

Any idea why the start button thread hangs while the other threads don't ?

Anonymous

4:15 PM

@JohnRennie I might need to do it once in an hour. Not a big deal :p

John Rennie

@Blue no idea. I have no knowledge of how Explorer has been written. MS don't release source code.

The page you linked seemed to be for W10 installations that had been upgraded from W7, so that wouldn't apply to you since you did a clean install.

Sir Cumference

Quick question. How did Newton figure out that air resistance was the cause for some objects falling slower than others? No one at the time knew about air molecules and it's completely invisible, so how'd he know that all objects would fall the same speed in a vacuum?

Anonymous

Heh. I should really take Bernardo's advice and shift to open source OS. :P lol

Anonymous

@SirCumference We don't really need to know about air molecules to figure that out...at least in a crude fashion

Anonymous

Air can be thought of as just another fluid

Sir Cumference

4:19 PM

@Blue Yes, but who knew that at the time?

Anonymous

@SirCumference I'm pretty sure that they knew air has behavior similar to fluids...

Sir Cumference

@Blue That doesn't seem likely

Anonymous

books.google.co.in/…

Sir Cumference

Huh. I stand corrected

Anonymous

Bernoulli and Newton lived at around the same time

Anonymous

4:24 PM

Bernoulli's principle is based on fluid/fluid flow which was very well applicable to air

Anonymous

centennialofflight.net/essay/Theories_of_Flight/early_aero/…

Anonymous

"
Scientists working in the 17th century contributed several theories relating to drag. The Italian mathematician and inventor Galileo Galilei built on Archimedes' work and discovered that the drag exerted on a body from a moving fluid is directly proportional to the density of the fluid. Density describes the mass of an object per unit volume. A very dense fluid produces more drag on objects passing through it than a less dense fluid. The density of air (a fluid) changes with its distance from the Earth's surface, becoming less dense the farther it is above the Earth's surface and, as such…

Anonymous

@SirCumference I don't see how...

Anonymous

@SirCumference In a more concrete manner, however, the concept of aggregates or units of bonded atoms, i.e. "molecules", traces its origins to Robert Boyle's 1661 hypothesis, in his famous treatise The Sceptical Chymist, that matter is composed of clusters of particles and that chemical change results from the rearrangement of the clusters.

Anonymous

Boyle argued that matter's basic elements consisted of various sorts and sizes of particles, called "corpuscles", which were capable of arranging themselves into groups.

Anonymous

4:31 PM

History of molecular theory

In chemistry, the history of molecular theory traces the origins of the concept or idea of the existence of strong chemical bonds between two or more atoms. The modern concept of molecules can be traced back towards pre-scientific and Greek philosophers such as Leucippus who argued that all the universe is composed of atoms and voids. Circa 450 BC Empedocles imagined fundamental elements (fire (), earth (), air (), and water ()) and "forces" of attraction and repulsion allowing the elements to interact. Prior to this, Heraclitus had claimed that fire or change was fundamental to our existence,...

Anonymous

Newton atleast had some idea that air consisted of elementary stuff (molecules)

Anonymous

C'mon...he developed the corpuscular theory of light! It would be funny if he didn't have atleast a crude idea about air molecules

Prathyush Poduval

@JohnRennie Hi, Do you know of any good books on non-equilibrium statistical mechanics?

John Rennie

@PrathyushPoduval no, sorry. I'm a bit out of touch with modern physics books so I'm not really the person to ask.

Prathyush Poduval

@JohnRennie Oh okay thanks

I'll ask ocelo or anyone else who come around then

Anonymous

4:44 PM

There is a NPTEL MOOC by Prof. Balakrishnan on nesm. He is a wonderful teacher...you might like it

Anonymous

I haven't gone through that MOOC myself though

Anonymous

But I liked his other MOOCs

Prathyush Poduval

@Blue I have gone through his classical mech course on youtube, but I didn't know about the stat mech one

Anonymous

nptel.ac.in/courses/115106091/1

Anonymous

@PrathyushPoduval Me too!

Anonymous

4:45 PM

I just found it now

Prathyush Poduval

I would prefer a good textbook, since I would have to watch the whole thing in the videos. But I see only one module in the lecture?

Anonymous

There are 36 lectures in it

Anonymous

I guess it covers a lot of topics

Anonymous

@PrathyushPoduval For books: Check the "references" tab

Anonymous

In the "syllabus" section

Prathyush Poduval

4:49 PM

@Blue Oh yeah, the lectures bar came down only now :P

@Blue Found it. I'll go through those books

Anonymous

Nice. I am taking a statistical mechanics course this sem. Perhaps I will go through those next sem

Anonymous

Our physics professor is awful though :P

Prathyush Poduval

Do it on your own then

Anonymous

@PrathyushPoduval I am

Prathyush Poduval

Berkley was a wonderful teacher

Anonymous

4:52 PM

Who's that?

Prathyush Poduval

I meant Berkley Physics Course :P

Anonymous

Oh...I should check them out

Prathyush Poduval

I'm also doing 2 of A Zee's books side by side (GTR and group theory)

His books are wonderful, anyone can understand it

Anonymous

Wow...great. :) Do them while you still have time. Once you are in college you'll be burdened with tests and other boring subjects.

Prathyush Poduval

Yeah, I have lots of time now since i don't have to worry about jee stuff. Moreover, I'm getting a month of holiday next month and plan on finishing a lot of physics then

Emilio Pisanty

5:11 PM

-3

Q: Cut off marks for various entrance exam

Can any 1 tell me the cut off of past few years for the following exams GATE JEST BARC & TIFR for Physics

education

Anonymous

Can't believe someone looking for graduate admission asking such questions on PSE instead of googling. omfg XD

0ßelö7

0

Q: Layman explanation of Hamiltonian Systems?

I've seen a lots of questions which has the word "Hamiltonian" in the title. I am curious to receive a simple explanation (if possible almost non-mathematical)for what actually is a Hamiltonian system or what is a Hamiltonian?

quantum-mechanics hamiltonian

Very Indian

Anonymous

@0ßelö7 I genuinely feel ashamed now. :P

0ßelö7

@Blue did you see that answer

She's probably Indian too

Anonymous

I did. And of course she is Indian.

0ßelö7

5:23 PM

I'm not racist against Indians...but damn son

Anonymous

I downvoted it. XD

Anonymous

@0ßelö7 Hmm. Such posts do reflect the general mindset towards academics here. Marks, marks, marks...and then Job, job, job...

Avantgarde

I gotta change my pic

Need more color

How about this

Anonymous

@Avantgarde cool :'D

Anonymous

I like the hanging mustache

2

Avantgarde

5:32 PM

It's not a moustache, but ok if that's what you wanna call it :P

0ßelö7

Ew

Avantgarde

Too dark?

yeah probably should change it

Anonymous

@0ßelö7 Says the guy with the creepiest profile pic...lol

Anonymous

@Avantgarde ^

Avantgarde

5:38 PM

Haha, is that a fashion brand?

Anonymous

A magazine

Avantgarde

I see

Very tacky

Anonymous

ITC Avant Garde

ITC Avant Garde Gothic is a font family based on the logo font used in the Avant Garde magazine. Herb Lubalin devised the logo concept and its companion headline typeface, and then he and Tom Carnase, a partner in Lubalin's design firm, worked together to transform the idea into a full-fledged typeface. The condensed fonts were drawn by Ed Benguiat in 1974, and the obliques were designed by André Gürtler, Erich Gschwind and Christian Mengelt in 1977. The original designs include one version for setting headlines and one for text copy. However, in the initial digitization, only the text design was...

Alex K Chen

Any ideas why curve has no attribute pos in vpython ? In the official website it's saying it should have.

Avantgarde

No idea

Alex K Chen

5:47 PM

@Avantgarde You have vpython in your pc ?

Avantgarde

@AlexKChen Nope

I meant that I didn't know the answer to your question

Sir Cumference

@Kaumudi.H I've fixed up the bugs with the starboard fixer, if you're interested. You can update it here.

0ßelö7

6:13 PM

@SirCumference we need to fix

Sir Cumference

@0ßelö7 ?

@0ßelö7 Want to hear a hilarious joke?

What would you be called if you were a spy? Double 0-celo-7

I'm so out of it...

Abcd

6:48 PM

How to obtain equilibrium sign (two half arrows) using MathJax? It's not given here: chemistry.meta.stackexchange.com/questions/86/…

Anonymous

Example: \ce{N2(g) + 3H2(g) <=>2NH3(g)}

Anonymous

You need to import the chem package

Abcd

@Blue What is chem package?

Anonymous

You can, of course, use \require{mhchem} in order to load mhchem as a one-off for the answer you are writing. E.g., $\require{mhchem} \ce{H20}$ . You only need to use \require{mhchem} once on the page. — Davide Cervone Aug 7 at 0:39

Anonymous

$$\require{mhchem} \ce{N2(g) + 3H2(g) <=>2NH3(g)}$$

Anonymous

6:52 PM

\require{mhchem} \ce{N2(g) + 3H2(g) <=>2NH3(g)}

0ßelö7

7:07 PM

Stop

No JEE

dmckee

@0ßelö7 Doesn't scan. "Hammer time" has three syllables and "No JEE" has either two or four. It just won't work.

Abcd

@0ßelö7 We didn't discuss anything related to JEE here.

Jaime Gallego

Kid disappears into the tesseract

►

0ßelö7

@dmckee what?

dmckee

7:37 PM

MC Hammer - U Can't Touch This

►

Sir Cumference

@dmckee Would you mind doing me a favor?

dmckee

Depends on the favor.

Sir Cumference

I'm working on an extension and I need to get some data about the mod diamond button in the topbar

Are you using Chrome?

dmckee

No I use firefox. And I'm not sure how much info about the diamond button the team wants out there.

You can find a lot of info that is already public on meta.stackexchange.

Sir Cumference

@dmckee I literally just need the size of it. I'm adding another button and I need the mod button's dimensions so that it doesn't overlap on it.

Would you be willing to check it, if I give you steps?

dmckee

7:43 PM

@SirCumference The inspector says 29 pixels. If I'm reading it right.

Sir Cumference

@dmckee That's for both the width and height?

dmckee

And if says the height is 34 pixels which is about the right aspect ratio.

Sir Cumference

@dmckee Huh. So the width is 29 pixels?

The other buttons have 34

dmckee

@SirCumference Just the element itself. I presume all the things up there use the same padding.

Sir Cumference

Are you counting padding, margins, etc.?

@dmckee And what's the width of the inbox?

dmckee

7:46 PM

36 pixels. Again, just the element.

And the diamond button is very narrow so that sounds right to me.

Sir Cumference

@dmckee Huh. You sure there's no extra padding?

dmckee

I don't speak CSS or any new flavor of html, so I'm not sure of anything.

Sir Cumference

@dmckee I have an idea. In the inspector, when you're selecting the mod button, click "computed"

That should show the padding/margin in a visual way

dmckee

@Secret That statement is far to strong. Theory is able to probe higher energies, but it still sucks at dealing with the kinds of moderate energies that are probed at JLAB. In the transition energy regime phenomenology continues to rule.

Sir Cumference

@dmckee Welp, I'll use that. Thanks a lot

dmckee

7:55 PM

52

A: Most ambiguous and inconsistent phrases and notations in maths

The inconsistent treatment of raising trig functions to powers: $$ \sin^n x \,.$$ Seriously, starting ab inito $$\sin^2 x$$ could mean either $$\sin( \sin(x) )$$ if you are a quantum mechanic and like to see everything as an operator or as $$(\sin x)^2$$ which is the conventional meaning. So wh...

Sir Cumference

@dmckee Sigh, forgot, can you tell me the id or class of the button so I know when to make this change?

For example, on the inbox, it'd say

Wait, actually, I might not need it

dmckee

topbar-icon icon-inbox-mod yes-hover js-mod-inbox-button

Sir Cumference

8:07 PM

@dmckee Thanks. I think I've figured it out tho

Sir Cumference

8:48 PM

I wish stackapps were still alive...

Semiclassical

something which I'm sure I once knew but don't now:

how does one do a Feynman slashed $\partial$ in TeX, e.g. in the Dirac equation?

Anonymous

15

Q: How do I draw a $\partial$ with a diagonal line through it?

As the title suggests, how do I draw a $\partial$ with a diagonal line through it?

math-mode symbols

Sir Cumference

9:11 PM

@dmckee shivers

Semiclassical

neat. doesn't seem to help in mathjax, but would be fine for actual tex documents

Sir Cumference

9:42 PM

@Blue Still causes confusion for Calc I students on what $d$ refers to

Sir Cumference

10:13 PM

MathJax test: $\text{test}$

Sigh, still isn't working

Ugh, forget it

Zophikel

10:51 PM

What's the perquisites for Lagrangian and Hamiltonian mechanics

16

Q: What exactly are Hamiltonian Mechanics (and Lagrangian mechanics)

What exactly are Hamiltonian Mechanics (and Lagrangian mechanics)? I want to self-study QM, and I've heard from most people that Hamiltonian mechanics is a prereq. So I wikipedia'd it and the entry only confused me more. I don't know any differential equations yet, so maybe that's why. But ...

quantum-mechanics newtonian-mechanics lagrangian-formalism hamiltonian-formalism

^ looking at this ?

dmckee

@Zophikel To work mechanically with them you need to be conversant with the notion of kinetic and potential energy and comfortable with partial derivatives.

Zophikel

@dmckee is that all the prequistes for Langurian Mechanics

?

dmckee

To develop them from the ground up calls for a little more familiarity with things like coordinate changes and the chain rule in a partial derivative context, but isn't much harder than that.

Zophikel

@dmckee anything else

?

dmckee

Introductions to the subject will typically be written assuming you are thoroughly familiar with a typical one-year introduction to Newtonian mechanics, and if you aren't you may have to back and fill a little along the way.

Zophikel

11:01 PM

dmckee is Newtonian Mechanics a prequiste I have no physics background I've done some computional mutivarible calculus

dmckee

Likewise they will typically assume you are familiar with the kind and level of mathematical argumentation that goes into multi-varient calculus and differential equations.

@Zophikel If you don't have Newtonian mechanics then you don't have the required knowledge of energies.

Zophikel

@dmckee hmmm that is true

i'm asking because I found some notes here that build everything form Newtonian mechanics

197.14.51.10:81/pmb/MECANIQUE/…

NeuroFuzzy

@AlexKChen Yep!!! try doing javascript on khanacademy!

@AlexKChen here's a bunch of stuff I wrote four or so years ago: khanacademy.org/profile/neurofuzzy/projects

Zophikel

@dmckee would those notes be good for a beginner ?

NeuroFuzzy

@AlexKChen and the add-on/extension ecosystem is just as good for javascript as for python. For example, I wrote this mathandcode.com/egun which makes use of numeric.js to solve Laplace's equation!

dmckee

11:07 PM

@Zophikel I'm not familiar with the Lewis book (and I would guess it is written from more of an engineering perspective than the books I am familiar with), but you can of course get to Lagrangian mechanics from Newtonian: that's how Lagrange got there, after all.

NeuroFuzzy

If you don't want to put them on the web then there are other options... but i'm probably not the best person to ask because i like doing things from scratch

(which usually means 2000 lines of code for some basic functionality XD)

Zophikel

@dmckee hmmmmm... that is true, what do you think the perquisites are for reading and going through those notes

Zophikel

11:24 PM

@dmckee because i'm initially asking because I did look at course webpages for the subject:

drps.ed.ac.uk/14-15/dpt/cxphys10015.htm

            ^ I saw nothing as Newtonian mechanics as a perquisite ?

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