stupid questions that don't deserve their own thread thread? I tried asking this on /adv/ and they sent me here instead. I need an android app that can help solve simultaneous equations involving complex numbers, if you wanna know why it's for solving alternate current circuits.

File: 114 KB, 1200x719, 1408540543286.jpg [View same] [iqdb] [saucenao] [google]

Anonymous Mon Mar 16 02:49:53 2015 No.7133383 [Reply] [Original]

stupid questions that don't deserve their own thread thread?
I tried asking this on /adv/ and they sent me here instead.
I need an android app that can help solve simultaneous equations involving complex numbers, if you wanna know why it's for solving alternate current circuits.

>>	Anonymous Mon Mar 16 04:48:15 2015 No.7133480 holy crap this took way much longer than it should have to any poor soul that sucks at googling like me, matrix reshish should be your best bet for complex numbers in linear algebra this is for the record for whoeever checks out the archive

>>	Anonymous Mon Mar 16 04:54:20 2015 No.7133485 Anyone major in physics and philosophy here? how hard is it? is it possible? should I even do it? >implying I won't do it anyway I just want people's opinions

>>	Anonymous Mon Mar 16 04:56:41 2015 No.7133487 >>7133485 obtaining a university degree is simple if you bother to put in the work. that mind sound obvious but the amount of worthless, lazy pieces of shit you will encounter in college will show you otherwise.

Anonymous Mon Mar 16 12:34:36 2015 No.7133915

>>7133383
Can anyone prove that the poisson approximation to the binomial distribution works? Namely that for a large sample size (say, n>50) and a small probability of success (such that np<5), the approximate poisson distribution will be distributed with mean and variance np?

>>	Anonymous Mon Mar 16 12:41:59 2015 No.7133921 >>7133485 Any major is doable if you're not retarded.

>>	Anonymous Mon Mar 16 12:43:40 2015 No.7133924 >>7133383 How did the phrase "of course" come about? Considering the definitions of the two words alone, I fail to see how it makes any sense.

>>	Anonymous Mon Mar 16 12:47:23 2015 No.7133929 >>7133924 Shortening of the phrase "of the ordinary course of events", Google is your friend, my friend. http://en.wiktionary.org/wiki/of_course

>>	Anonymous Mon Mar 16 12:49:01 2015 No.7133930 >>7133915 Take the limit as number of events goes to infinity and keep the probability of success in each small time interval constant, which means that the time interval goes to zero as expected. Be careful with limits

>>	Anonymous Mon Mar 16 12:52:20 2015 No.7133935 >>7133930 Doesn't the binomal distribution assume a constant number of events?

Anonymous Mon Mar 16 12:55:23 2015 No.7133944

In exactly one year I will be required to pass calculus one in order to stay in my major of choice. At the moment I do not have a full understanding of basic introductory algebra. Realistically, how hard will this be to do and is calc 1 really all that difficult if I can get a good understanding of algebra down?

>>	Anonymous Mon Mar 16 12:55:53 2015 No.7133945 What would happen to mathematics if the concept of infinity was not used? Would we still be able to get accurate calculations similar to how Archimedes used the method of exhaustion? Or are some things just "impossible" without infinity?

>>	Anonymous Mon Mar 16 13:02:52 2015 No.7133957 >>7133935 call events n, call probability p np is the expected number of success (if you try something 10% 100 times, you expect to succeed 10 times) if you keep np constant but make p->0 n->inf, it will be poisson distribution

Anonymous Mon Mar 16 13:03:19 2015 No.7133958

>>7133944
Calc I is easy, my friend. If you are a dumbfuck you don't even have to understand it (though, obviously, it's better in every way if you do), it's enough to just memorise the formulas and do exercises like a fucking nigger in a cotton field until you know every single one of them by heart. As far as algebra goes, the hardest thing you'll ever do is polynomial factorisation while you're working with limits (again, exercises like a motherfucker).

This is all assuming you'll ONLY take Calc I, if you deal with anything more advanced, then you'll definitely a firmer understanding of it all.

>>	Anonymous Mon Mar 16 13:15:55 2015 No.7133978 >>7133957 Excuse me for my obvious lack of knowledge of statistical theory, but why does letting p tend to 0 and n tend to infinity give a poisson distribution?

>>	Anonymous Mon Mar 16 13:17:43 2015 No.7133984 File: 82 KB, 643x624, electromagnetic waves.png [View same] [iqdb] [saucenao] [google] I've illustrated my understanding of EM radiation in pic related, can someone tell me where i got it wrong and why?

>>	Anonymous Mon Mar 16 13:23:43 2015 No.7133998 >>7133984 without getting to the math of it, you have an okay understanding id say

Anonymous Mon Mar 16 13:24:20 2015 No.7133999

>>7133958
What the actual fuck, brit-fag here, I just took a look at the Calc 1 spec, do you guys really do all the stuff on the Pauls' notes page in 6 months? Fair enough at that being uni level, but in britfagland, we do all that in two years of college, and that's only if you take maths as two of your three/four subjects, otherwise you wouldn't have covered all that shit until doing 2 years of college and then like half a year of uni (though of course, while doing this we cover a shittonne of other maths, but fuck me I'd like more than 6 months for what I see as 2 years of calculus to sink in).

>>	Anonymous Mon Mar 16 13:28:35 2015 No.7134005 >>7133998 I would really like to get into the math, what level of calculus should I study?

Anonymous Mon Mar 16 13:30:46 2015 No.7134007

>>7133978
using regular binomial distribution you have a finite number of n. you can show them on a bar graph
because when you have infinite n and infinitesimal p, you have as many n as real numbers so you cannot show it as a bar graph, it has to be a continuous function
you might know that the taylor expansion of e^x has factorials in its denominator, through the magic of mathematics, when you take that limit you obtain the poisson distribution

>why does letting p tend to 0 and n tend to infinity give a poisson distribution?
you can't ask the question "why" in math/science

if you want to see the derivation, look for it online, no one will latex it here

>>	Anonymous Mon Mar 16 13:38:51 2015 No.7134018 >>7134005 No calculus. You need vector analysis.

Anonymous Mon Mar 16 13:39:19 2015 No.7134019

>>7134005
as hilarious as that question normally would seem, you don't need calculus to understand electromagnetic "PLANE WAVES" (which is the thingy you drew at the bottom of your image)
i'm guessing you are a highschool student, you can learn about electromagnetism in physics or electrical engineering, there is no point in rushing
otherwise why would you care about the math of it, if you were "just curious"
if you only wanted to know about plane electromagnetic waves, it is very light on math however you need a lot of background to understand why any of those methods work

Anonymous Mon Mar 16 13:54:38 2015 No.7134040
File: 33 KB, 457x193, simmat.jpg [View same] [iqdb] [saucenao] [google]

How do I go about testing whether or not two 2x2 matrices are similar? (http://en.wikipedia.org/wiki/Matrix_similarity)) My linear algebra book lists some conditions that are necessary (pic related), but I don't think any of these are sufficient? The excercises in the book are simple, because the ranges are inequal and thus the answer is no, but this is not the case here. Any pointers?

>>	Anonymous Mon Mar 16 14:15:16 2015 No.7134069 >>7134018 This basically called calc 4 in most unis

>>	Anonymous Mon Mar 16 14:18:52 2015 No.7134075 >>7134069 i dont want to bash the education system but it is fuckin vile that it takes 2 years to bring someone up to vector calculus

>>	Anonymous Mon Mar 16 14:24:09 2015 No.7134084 >>7134040 why not ask your teacher

>>	Anonymous Mon Mar 16 14:43:47 2015 No.7134125 Do you guys have any tips on how to memorize formulas quickly and efficiently?

>>	Anonymous Mon Mar 16 14:47:59 2015 No.7134129 >>7134125 no my only advice would be to loathe your teacher for not allowing a cheat sheet in the exam

Anonymous Mon Mar 16 14:52:35 2015 No.7134141

>>7134125
If guy understand the base formula really well and you could derive it in the exam easily. However if it is a messy process then just do a lot of practice with the particular formula you are having trouble doing mindless problems (basically pluggin values into the equation) but always writting down in paper the process. It is tedious but you will remember it. But usually, at least in a good program, formulae that isn't basic and quite specific for a particual thing should be given and other skills should be tested, but teachers are lazy.

If girl, go with your friends and do rhyming songs, wordplays and memes. It is quite cringy though

>>	Anonymous Mon Mar 16 15:15:52 2015 No.7134171 >>7134040 Same characteristic and minimal polynomial.

>>	Anonymous Mon Mar 16 16:10:59 2015 No.7134288 Does vacuum have resistance? just making sure

>>	Anonymous Mon Mar 16 16:49:24 2015 No.7134370 >>7134288 yes 377 ohms

>>	Anonymous Mon Mar 16 16:50:36 2015 No.7134375 >>7133383 Is there anyway to do anything about a suspicious of lifelong male anorgasmia? The best advice I can find online is "see a doctor and/or get Viagra". >>7134288 What sort of resistance? The answer's probably no.

>>	Anonymous Mon Mar 16 16:57:33 2015 No.7134391 File: 9 KB, 251x241, 1424542424815.jpg [View same] [iqdb] [saucenao] [google] >>7134370 People are going to think this is a bullshit arbitrary answer. lel.

>>	Anonymous Mon Mar 16 17:04:24 2015 No.7134403 >>7134370 bullshit

>>	Anonymous Mon Mar 16 17:11:01 2015 No.7134414 >>7134370 >>7134391 >>7134403 haha expected this https://en.wikipedia.org/wiki/Impedance_of_free_space#Exact_value of course anyone who knows the existence of such a value would know what it is good for

>>	Anonymous Mon Mar 16 17:13:10 2015 No.7134418 >>7134414 It's not accurate (or at least very misleading) to say that's the "resistance of vacuum" though.

>>	Anonymous Mon Mar 16 17:16:11 2015 No.7134427 >>7134370 >377 ohms only true for 0 kelvin. Else its 377 ohms * exp(-alpha T) with alpha being the universal thermal vacuum constant and T the absolute temperatur in Kelvin

>>	Anonymous Mon Mar 16 17:18:35 2015 No.7134430 >>7134418 that is true, i just wanted to give a surprising answer

>>	Anonymous Mon Mar 16 17:20:34 2015 No.7134433 >>7134427 how do you even measure the temperature of vacuum

>>	Anonymous Mon Mar 16 17:25:32 2015 No.7134442 File: 24 KB, 1040x226, grades.png [View same] [iqdb] [saucenao] [google] How does a stupid person learn Calculus II and Physics? And Chemistry too. In as little time as possible.

Anonymous Mon Mar 16 17:28:50 2015 No.7134446

>>7134433
>how do you even measure the temperature of vacuum
in 1946 simon eventer "developed" (he came up with the idea, but technology wasnt ready yet, similiar to the first transistor) a sensor called universal eventer celtimeter (the last part is a mixture of celcius and meter, though of course it uses kelvin) which was actually build around 1980s that used vacuum flucuations to measure what is called the "vaccuums temperature". hard to find info on it using google as it is a VERY specific tool only used in a certain area of astrophysics

>>	Anonymous Mon Mar 16 17:29:54 2015 No.7134453 >>7134442 >In as little time as possible. by just doing it. your brain adjusts, just spend your time on it and not on 4chan

Anonymous Mon Mar 16 17:36:12 2015 No.7134470

>>7134442
you attend the lectures
you find the solution manual of the textbook you are using
google "*name of the book* solution manual pdf"
if a manual does not exist, find a good book that has a manual (i don't know off the top of my head you need to search for it)
do all the end of the chapter problems
it is more important to have seen all the problems than to spend 1 hour per question. dont be afraid to look at the solutions, but it is important that you understand the solutions

DO NOT take advice from mathfags/proovefags on /sci/
those motherfuckers be lying and gettin me pissed
they will advice you to do useless shit that will not help you in your exams

>>	Anonymous Mon Mar 16 17:38:19 2015 No.7134472 >>7134446 >universal eventer celtimeter uhhh, is that by any chance some power bracelet tier pseudoscience? I never saw such a formula * exp(-alpha T)

Anonymous Mon Mar 16 17:44:06 2015 No.7134482

>>7134472
>uhhh, is that by any chance some power bracelet tier pseudoscience?
i will ask my professor whether what he is using is "bracelet tier pseudoscience". I will return with his reply.

>I never saw such a formula
> * exp(-alpha T)
? what do you mean? exp(-ax) is just an exponential function. This special one is simply used in a rather small area of theoretical vacuum electrodynamics. Mind though that is just an approximation for infinite homogenous current densities. the general formula is rather complex.

Anonymous Mon Mar 16 17:49:49 2015 No.7134493
File: 34 KB, 752x862, questions.png [View same] [iqdb] [saucenao] [google]

In addition to the second question, (If A is correct) If there were a magnet inside the magnetic cylinder, would the cylinder exert a force on it? I know this might be a really stupid question but I'm just making sure I don't have any misconceptions about this

Anonymous Mon Mar 16 18:00:18 2015 No.7134510

>>7134482
google returns with nothing on simon eventer, universal eventer celtimeter, universal thermal vacuum constant
so i doubt the validity of what yo have said

>>7134493
would "what" cause the metal core to rotate/move?
transformers are known to hum at the frequency of AC. sound=movement

is the cylinder ferromagnetic? if so, the inside of the cylinder may be shielded from the effects of the current. otherwise you would have an electromagnet and it will exert a force on the magnet.

>>	Anonymous Mon Mar 16 18:01:57 2015 No.7134513 >>7134510 it's running on DC according the pic

>>	Anonymous Mon Mar 16 18:03:26 2015 No.7134519 >>7134513 the transformer clearly says ac the cyclinder, it doesnt really matter

>>	Anonymous Mon Mar 16 18:04:09 2015 No.7134522 >>7134510 > the inside of the cylinder may be shielded from the effects of the current. otherwise you would have an electromagnet and it will exert a force on the magnet. why?

>>	Anonymous Mon Mar 16 18:05:16 2015 No.7134523 >>7134519 shit I fucked up, it was supposed to say DC

>>	Anonymous Mon Mar 16 18:07:15 2015 No.7134530 >>7134510 >google returns with nothing on simon eventer, universal eventer celtimeter, universal thermal vacuum constant >so i doubt the validity of what yo have said well it was convincing enough for you to google ahahahahahahahaha

Anonymous Mon Mar 16 18:11:01 2015 No.7134536

>>7134522
ferromagnetic material (high µ) have a strong affinity for magnetic fields, they suck all the magnetic field lines so there wont be any magnetic field left for the middle of the cylinder.

>>7134523
it wouldnt move

>>7134530
hahaha i love you. i had a good laugh

Anonymous Mon Mar 16 18:12:33 2015 No.7134540

>>7134141
>If guy understand the base formula really well and you could derive it in the exam easily.

I haven't found deriving stuff in exams to be necessary. If you understand the base concepts and where the formula comes from, it's much easier to remember. It's like memorizing a sentence in your native language versus memorizing a string of random letters.

>>	Anonymous Mon Mar 16 18:18:04 2015 No.7134548 >>7134171 thanks, I think that'll get me somewhere

Anonymous Mon Mar 16 18:19:06 2015 No.7134551
File: 1.88 MB, 2448x3264, IMG_2060.jpg [View same] [iqdb] [saucenao] [google]

>>7134540
this was my cheat sheet for intro to quantum mech i took few years ago
you cant remember this shit
I got A+ and I had too look to my cheat sheet for practically everything
I would have to memorize all those shit as if i were memorizing a theater role or someshit
it is UNJUSTIFIABLE SCUMBAGGARY for teachers not to allow cheatsheets in exams

Anonymous Mon Mar 16 18:20:13 2015 No.7134555
File: 19 KB, 636x964, questions1.png [View same] [iqdb] [saucenao] [google]

>>7134536
>ferromagnetic material (high µ) have a strong affinity for magnetic fields, they suck all the magnetic field lines so there wont be any magnetic field left for the middle of the cylinder.

so what will the magnetic field look like?

>>	Anonymous Mon Mar 16 18:22:12 2015 No.7134559 File: 16 KB, 285x288, 1386036415879.jpg [View same] [iqdb] [saucenao] [google] >>7134555 chekt what the hell is that image supposed to be direct current wound metal core? i don't really think the outer field lines would change

>>	Anonymous Mon Mar 16 18:30:46 2015 No.7134572 >>7134559 you said there wouldn't be any magnetic fields left in the middle what about the outer magnetic fields of the magnetic cylinder?

>>	Anonymous Mon Mar 16 18:34:14 2015 No.7134578 >>7134572 honestly i do not know, i doubt there would be a significant change

>>	Anonymous Mon Mar 16 18:35:04 2015 No.7134579 Do a radio wave or a laser travel in space forever? (unless they hit something, of course) If yes, are they immune to entropy?

>>	Anonymous Mon Mar 16 18:35:49 2015 No.7134581 >>7134578 change in what

>>	Anonymous Mon Mar 16 18:38:24 2015 No.7134584 >>7134581 how the field lines look outside of the core >>7134579 >Do a radio wave or a laser travel in space forever? (unless they hit something, of course) why wouldn't it wave has an energy and it cant just disappear into nothingness

>>	Anonymous Mon Mar 16 18:41:04 2015 No.7134586 >>7134584 What about entropy? A wave is a way of "organizing" energy, isn't?

>>	Anonymous Mon Mar 16 18:42:41 2015 No.7134587 >>7134586 i know jack shit about entropy also i doubt you know any better than i (meaning you probably don't even know what the entropy question really means)

>>	Anonymous Mon Mar 16 18:44:50 2015 No.7134591 >>7134587 I don't know much, that's why I'm asking and not answering. Just shut the fuck up

>>	Anonymous Mon Mar 16 18:49:01 2015 No.7134603 File: 36 KB, 730x600, 730px-Kyubey.jpg [View same] [iqdb] [saucenao] [google] >>7134586 >>7134587 >>7134591 >entropy lel entropy is a meme science, it isn't a real thing

>>	Anonymous Mon Mar 16 19:21:44 2015 No.7134648 >>7134603 I was walking around my college and one of the professors doors said "Director of Entropy". I still wonder about that.

>>	Anonymous Mon Mar 16 19:25:28 2015 No.7134653 >>7134648 make a contract with him

>>	Anonymous Mon Mar 16 20:06:15 2015 No.7134705 >>7133945 >I posted this 7 hours ago >nobody responded to it t-thanks

>>	Anonymous Mon Mar 16 20:16:27 2015 No.7134720 >>7134705 thats because you asked a weird fuckin question

Anonymous Tue Mar 17 13:29:37 2015 No.7135847

>>7134705
The Greeks deliberately avoided algebra and infinity because they fucked each other up, so as a minimum, you can get as far as the Greeks.

From my own experience, I'd say that statistics would be near-impossible but that's mostly just because you've kinda fucked calculus. Otherwise I don't know.

>>	Anonymous Tue Mar 17 13:33:15 2015 No.7135855 >>7134705 >no riemann sum DO YOU WANT TO LIVE IN A WORLD WITHOUT TRIPLE INTEGRALS?

Anonymous Tue Mar 17 14:34:07 2015 No.7135960

>>7133383
Is there an efficient way to split stuff like
<span class="math"> \frac{x^4}{(x^2+4)(x-2)^2} [/spoiler] into partial fractions? While I'm certainly capable of doing it, I can't seem to do it quickly, any tips? (or heck, just showing me any method that can do it in less than half of a post would probably be more than sufficient)

>>	Anonymous Tue Mar 17 14:47:12 2015 No.7135994 File: 1.94 MB, 2448x3264, IMG_2064.jpg [View same] [iqdb] [saucenao] [google] >>7135960 uhh, you'll never need to do that out of calculus class this is the easiest way you'll ever do it

>>	Anonymous Tue Mar 17 15:04:10 2015 No.7136017 >>7134414 Dem planar waves tho

>>	Anonymous Tue Mar 17 15:17:32 2015 No.7136033 >>7133945 You can't plot tan(x) = <span class="math">\frac{sin(x)}{cos(x)}[/spoiler] without accepting that tan(90) = infinity

>>	Anonymous Tue Mar 17 15:24:24 2015 No.7136049 >>7136033 >= infinity inb4 mathfags flip their shit

Anonymous Tue Mar 17 15:33:10 2015 No.7136072

>>7136049
I remember my teacher showing us sec, cosec and cot functions.
She spent a good while explaining that because 1/0 is undefined, tan(90) is undefined, so cot(90) is also undefined.
She made us draw the plot with a little gap at the origin because "it is really going through it".

Meanwhile the entire class is looking at the graph saying it's clearly just 0.
So that was the day I decided engineering math is best math.

>>	Anonymous Tue Mar 17 15:34:55 2015 No.7136075 >>7136072 isn't really*

>>	Anonymous Tue Mar 17 15:40:36 2015 No.7136084 >>7136072 hahahahah what a scrub cot isnt even defined as 1/tan, it is cos/sin

>>	Anonymous Tue Mar 17 18:12:44 2015 No.7136533 File: 1.14 MB, 1936x2592, photo.jpg [View same] [iqdb] [saucenao] [google] Can anyone help me with pic related? How do i calculate f'(0) and f'(1)? Pls

>>	Anonymous Tue Mar 17 18:17:03 2015 No.7136546 >>7136533 It's staring you in the face anon, even if you can't see the easy way then you can just work out what one big square covers.

>>	Anonymous Tue Mar 17 18:17:29 2015 No.7136547 >>7136533 1- HIGHSCHOLER GET OUT 2- f'() means the slope of a tangent at that point the tangent line is drawn for f(0) you need its slope what about the tangent line at f(1) what will it look like do you think?

>>	Anonymous Tue Mar 17 18:19:41 2015 No.7136557 >>7136533 f'(1) = 0 cuz global max f'(0) = slope of the line drawn = 1

Anonymous Tue Mar 17 18:20:16 2015 No.7136559

>>7136547
...Since when was calculus, even basic calculus like that shit, high school? ...I don't understand the American system... and there's probably a better way than considering the tangents, I'd probably go for the maxima argument or even just say "lol use the pleb-teir capital delta y over capitical delta x method".

>>	Anonymous Tue Mar 17 18:22:38 2015 No.7136567 >>7136533 >Can anyone help me with pic related? How do i calculate f'(0) and f'(1)? >Pls what kind of graph is this? like which function do you know who has a similiar one

>>	Anonymous Tue Mar 17 18:23:37 2015 No.7136573 >>7136567 Dude... if he can't solve that I doubt he'll be able to tell you the answer... are you trying to bait him into using the factor theorem?

>>	Anonymous Tue Mar 17 18:27:09 2015 No.7136584 >>7136559 i don't know about american system but differentiation is highschool 3 (out of 4 years) in my country

>>	Anonymous Tue Mar 17 18:28:40 2015 No.7136590 >>7136584 In my country, high school lasts 6 years, and calculus isn't covered until the college equivalent...

>>	Anonymous Tue Mar 17 18:29:56 2015 No.7136596 >>7136584 uk does calculus from 16

>>	Anonymous Tue Mar 17 18:34:54 2015 No.7136614 File: 416 KB, 1080x894, Flag_-_Union_Flag.jpg [View same] [iqdb] [saucenao] [google] ...I'd like to declare my eternal support for my country's effort to keep high schoolers off /sci/ by not teaching calculus until age 16.

Anonymous Tue Mar 17 18:46:50 2015 No.7136646
File: 48 KB, 460x476, even-after-first-question-248.jpg [View same] [iqdb] [saucenao] [google]

>>7136547
>>7136557
Can you explain how it's done? Ok it's the slope of the tangent we're trying to get here. But shouldn't f'(0) make us stay on 0X since it says 0?

>>	Anonymous Tue Mar 17 18:49:20 2015 No.7136656 >>7136646 THE SLOPE OF THE LINE THE SLOOPPPPEEEE

>>	Anonymous Tue Mar 17 18:51:14 2015 No.7136660 File: 31 KB, 318x322, 1395399750485.jpg [View same] [iqdb] [saucenao] [google] >mfw since posting

>>	Anonymous Tue Mar 17 18:52:37 2015 No.7136663 >>7136646 do you even know what a fuckin slope is

Anonymous Tue Mar 17 18:54:33 2015 No.7136669

>>7136614
...let it never be said that the British are unkind, I'll deal with this shit.

f'(0) is the gradient of the tangent to the curve at the point x=0. By that, I mean the gradient of tangent of the fucking line that's drawn on the fucking paper.

If you're old enough to understand what the word "fucking" means, then I've told you enough to do the question.

>>	Anonymous Tue Mar 17 18:55:58 2015 No.7136674 File: 1.17 MB, 1936x2592, photo - Copy.jpg [View same] [iqdb] [saucenao] [google] >>7136663 What's circled in red is what we call slopes

>>	Anonymous Tue Mar 17 18:57:10 2015 No.7136677 >>7136674 so basically you have no idea what it means

>>	Anonymous Tue Mar 17 18:57:21 2015 No.7136679 >>7136669 Thanks. Got it know. I'll see myself out. I'll be back when i get into a university. >if i can make it up the slopes

>>	Anonymous Tue Mar 17 18:58:24 2015 No.7136680 File: 30 KB, 251x236, 1330289926162.jpg [View same] [iqdb] [saucenao] [google] >>7136674 are you a magnet?

>>	Anonymous Tue Mar 17 18:59:25 2015 No.7136684 >>7136680 I can't even potato right now man.

>>	Anonymous Tue Mar 17 19:14:58 2015 No.7136711 >>7136684 Never go full potato

>>	Anonymous Wed Mar 18 04:16:21 2015 No.7137456 File: 20 KB, 449x351, 031715.png [View same] [iqdb] [saucenao] [google] Can anyone knowledgeable about fluid dynamics help me with this problem? I don't have any clue about how to even approach this.

>>	Check em Wed Mar 18 04:30:09 2015 No.7137475 >>7137456 >Mathematics im a math major and i think i cna do this

>>	Anonymous Wed Mar 18 04:37:24 2015 No.7137482 Say, where does the root of x=0 come from in f'(x) = e^(-x) * (9x^2 - 3x^3)? I get x=3 from the second part of the function, and think e^(-x) has no roots, but wolfram's tellin me there's another.

>>	Anonymous Wed Mar 18 04:50:33 2015 No.7137496 is anyone able to explain pic related to me? if we have a domain m and a codomain k and we dont know their size relative to one another, how can we count the amount of surjective functions?

>>	Anonymous Wed Mar 18 04:55:17 2015 No.7137506 File: 391 KB, 2901x649, DSC_0007.jpg [View same] [iqdb] [saucenao] [google] >>7137496 forgot pic related

>>	Anonymous Wed Mar 18 04:57:21 2015 No.7137508 >>7137506 i failed that class

>>	Anonymous Wed Mar 18 04:58:02 2015 No.7137509 >>7137508 discrete maths? im feeling a fail too it's week 3 and we're into inclusion/exclusion principles and i'm getting blown the fuck out haha

Anonymous Wed Mar 18 05:24:31 2015 No.7137521

>>7137506
This is inclusion-exclusion.

Lets think about what a surjective function is. It maps every x to a certain y, called f(x), and every y must be hit. So we are looking at the set S of all f such that

y_j \in f(X) for all j=1 ...k

i.e. y_j is hit by f for all j

Where we label the y \in Y as y_j. Now by de-Morgan's laws, we can think of S as the set of all f such that

there is no j such that y_j is not hit by f

This is of the form of a union of sets of the form

{ f | y_j is not hit by f \}^c

We can then use inclusion-exclusion. Is this a good enough hint?

Anonymous Wed Mar 18 05:31:02 2015 No.7137526
File: 60 KB, 1465x491, Capture.jpg [View same] [iqdb] [saucenao] [google]

>>7137521
still reading through your comment but did you use the inbuilt latex to format your stuff? it isn't coming up for me if you did

is it possible to screen cap and post the screen cap?

thanks btw

Anonymous Wed Mar 18 05:41:30 2015 No.7137535

>>7137526
No, I don't know how to tell /sci/ to use a TeX environment and am too lazy to learn.

Anyways, the key is to realize that you have

k^m functions in total

you want to subtract the functions who miss 1 element. To miss one element you first need to choose that element. That is (k choose 1) choices. Then for each such choice you still have to choose the functions, and since 1 element is out, there are (k-1) remaining, leading to (k-1)^m choices. so we are led to subtract

(k choose 1)(k-1)^m

but wait! we need to add in all the terms which miss 2 elements, or else we'd double-count. then we'd subtract the ones that miss 3, add the ones which miss 4, and so on.

Maybe this less formal analysis helps you.

>>	Anonymous Wed Mar 18 05:48:10 2015 No.7137542 >>7137535 >you want to subtract the functions who miss 1 element. because if you miss one element it cant be surjective?

>>	Anonymous Wed Mar 18 05:51:20 2015 No.7137544 >>7137535 >>7137542 sorry i just dont really understand why it is that we do (k choose 1) - why a combination? and why do then go to 2, 3, 4, etc? sorry to take up your time

Anonymous Wed Mar 18 06:04:11 2015 No.7137551

>>7137542
yes. to be surjective, we can't miss ANY elements.

>>7137544
we do (k choose 1), because we need to do 2 things:

1) choose which element to miss
2) figure out what functions can miss it

the first is (k choose 1) because we are choosing 1 element out of k

the latter is (k-1)^m because we have (k-1) elements to map TO, and m elements to map to them.

the reason we add on 2, etc., is because if a function misses 1 element, then it could ALSO miss 2 elements. so we need to count up the ways to miss 2 elements, and account for this.

read
http://en.wikipedia.org/wiki/Inclusion%E2%80%93exclusion_principle#Statement

we are using the 'complementary form' at the bottom of that section.

The sets A_j represent the functions which miss y_j. We are interested in the functions which do not lie in ANY of the A_j. That is, functions who are in the intersection of the complement of the A_j, which is what the formula gives us.

>>	Anonymous Wed Mar 18 06:14:13 2015 No.7137558 >>7137551 i can of get it now thanks mate

>>	Anonymous Wed Mar 18 06:15:08 2015 No.7137560 >>7137558 glad i could help :)

Anonymous Wed Mar 18 07:29:42 2015 No.7137634
File: 18 KB, 512x339, profus.gif [View same] [iqdb] [saucenao] [google]

Question:
Can diprotons exist? Even for a tiny tiny fraction of a fraction of a second before decaying? Otherwise, how does proton-proton fusion occur? (yeah i know a proton beta+ decays, but you gotta get the protons together first, right?)

Anonymous Wed Mar 18 07:49:29 2015 No.7137643

>>7133383
I guess I'll just use this thread because my question is probably very embarrassing for anyone with any kind of formation in the area.
It's about the speed of light. I've learned that the speed of light is constant no matter the perspective, and that light will go the same speed regardless of the movement of the initial release.
According to this, is it true then that the actual speed of light on Earth (at my house for example) would be
c minus the Earth's speed around the Galaxy?
My question really is, if c is the max amount of speed possible for light, is it true that light's speed on Earth would be smaller because of the Earth's own movement around the Galaxy (which would be Sun + solar system etc.)?

>>	Anonymous Wed Mar 18 07:58:28 2015 No.7137653 File: 14 KB, 375x145, Capture.jpg [View same] [iqdb] [saucenao] [google] how do i figure out a stirling triangle number? e.g. the 7 at (4,2)

>>	Anonymous Wed Mar 18 08:00:44 2015 No.7137654 >>7133485 As long as you just work. I haven't studied physics but compared to law, books on philosophy isn't as big but they're denser.

>>	Anonymous Wed Mar 18 08:08:42 2015 No.7137663 >>7134375 Ok. An injection of papaverine, increased mechanical stimulation will determine mechanics, after that, psychology.

>>	Anonymous Wed Mar 18 08:38:56 2015 No.7137687 File: 1.41 MB, 2000x1358, Tropical_cyclones_1945_2006_wikicolor.png [View same] [iqdb] [saucenao] [google] K, I gotta stupid question. Why South America gets no hurricane love? Are they all hurriphobic cyclophobes?

>>	Anonymous Wed Mar 18 09:05:10 2015 No.7137706 File: 790 KB, 792x792, yhy.png [View same] [iqdb] [saucenao] [google] >>7137456 bump on this

>>	Anonymous Wed Mar 18 09:25:53 2015 No.7137732 >>7137456 gema gema pushuu that sounds like a fuckin anime thing can you say that the gema discharges all the water in 10 seconds in constant flow? otherwise I don't see how this can be solved

>>	Anonymous Wed Mar 18 09:28:07 2015 No.7137735 >>7137456 also is this from an actual textbook? i have never seen someone reveal his powerlevel in such grandeur

>>	Anonymous Wed Mar 18 10:45:35 2015 No.7137845 What's the ratio of Sun-like stars in the universe?

>>	Anonymous Wed Mar 18 11:03:39 2015 No.7137860 In a mixed integer program, how can get set a binary variable to 1 iff a certain real variable is greater than another?

>>	Anonymous Wed Mar 18 11:04:52 2015 No.7137861 >>7137860 In addition, both those real variables are positive.

>>	Anonymous Wed Mar 18 11:23:10 2015 No.7137882 how can I get the values of a point of a Mathematica plot as I would in Matlab. In matlab, I can hold my mouse on the plot and it would show me the values but I cant seem to be able to do it on mathematica

>>	Anonymous Wed Mar 18 11:45:03 2015 No.7137919 Is muon catalyzed fusion still being researched or is it dead in the water

Anonymous Wed Mar 18 13:22:24 2015 No.7138075

>>7137634
It's kind of like the super heavy elements. It's just too unstable to stick around for long enough to consider it as anything other than a process.
For stability we generally graph the proton/neutron ratio, and aim for this ratio to be pretty close to 1, the exception being hydrogen.

Hydrogen is already unstable as fuck, doubling the proton-rich nucleus is not going to help

>>	Anonymous Wed Mar 18 13:33:25 2015 No.7138093 >>7137706 Basic water flow equation mate. You find pressure by assuming water volume, then mass, then area through orifice with time, then use the standard flow equation thing. We did that in Physics 1 or 2 with calc.

Anonymous Wed Mar 18 13:45:33 2015 No.7138110

If taking the derivative of a function gives you an expression of how much the function value changes per x, then why is the inverse the area under the curve? How are the two related?

I can derive the derivative from infinitesimals and tangents and whatever. And I can derive integrals by doing Riemann sums.

But I have not yet seen a proof that is not circular or autistic.

Anonymous Wed Mar 18 13:49:04 2015 No.7138114

>>7138110
You're probably not seeing the idea properly. The derivative and the integral are not just arbitrary algorithms, they're new functional concepts, like exponents and logs.

Integrals add up all changes, derivatives are those changes. What's your problem?

>>	Anonymous Wed Mar 18 13:50:15 2015 No.7138120 How do I integrate sin(x)/x

>>	Anonymous Wed Mar 18 13:54:22 2015 No.7138127 Is l'Hôpital's rule supposed to replace any and all methods for finding the limits to problems when there's an indeterminate?

>>	Anonymous Wed Mar 18 13:56:41 2015 No.7138133 LET ME TELL YOU SOMETHING BO, A PHYSISIST ASKS WHY BUT AN ENEGENIR ASKS HOW??? WHO ARE YIU HUH?

Anonymous Wed Mar 18 14:36:03 2015 No.7138201

>>7138110
There is no "proof" because integrals and derivative functions are not measurable constants like e or pi.
The "proofs" are circular because we ourselves have defined what those functions mean.

If you have a baby, and name it Andy, and someone asks why his name is Andy and you say "because that's I called him" is that circular logic?

It's a definition m8, learn the fucking difference. From that definition we create proofs to find equivalences GIVEN that definition.

>>	Anonymous Wed Mar 18 15:07:44 2015 No.7138264 >>7138133 a physicist never asks why science is by definition unable to answer the question of why

>>	Anonymous Wed Mar 18 15:18:03 2015 No.7138285 Is calculus a part of Mathematical Analysis or are the two terms synonymous?

>>	Anonymous Wed Mar 18 15:23:49 2015 No.7138295 >>7138285 "Real analysis" is rigorous calculus.

>>	Anonymous Wed Mar 18 15:24:32 2015 No.7138299 >>7138127 >replace It doesn't replace a damn thing m8. You use it for indeterminate forms of differentials that fit whatever exact forms, like 1^inf, 0/0 or somethin.

>>	Anonymous Wed Mar 18 15:26:42 2015 No.7138305 Graph theory problem. How can I show that the number of edges in an induced matching can not be greater than the size of a maximum independent vertex set?

>>	Anonymous Wed Mar 18 15:56:37 2015 No.7138380 >>7138305 I feel this should be pretty easy.

Anonymous Wed Mar 18 16:11:46 2015 No.7138411

>>7137732
>>7137735

It's from an anime knowledge quiz, was hoping a bro could help me out since the last time I practiced physics and calc was in high school. There are other stupid questions as well that involves differential equations, fractals, and vectors that took me some time, but this was the only question that I'm not able to do

Anonymous Wed Mar 18 16:20:17 2015 No.7138435

>>7137456
total water volume inside is
4/3*pi*(12.5^3-1.5^3)=8167ft^3
ASSUMING CONSTANT FLOW
816.7ft^3/s
the surface area of the oriface
pi*(1.25)^2=4.91ft^2
speed
816.7/4.91=116.3ft/s=50.7m/s
v^2/(2a) := maximum altitude, a=9.8m/s^2
131.1m=430.1ft
if we cant assume constant flow, we cant solve it

>>	Anonymous Wed Mar 18 16:26:52 2015 No.7138455 File: 122 KB, 650x487, link.jpg [View same] [iqdb] [saucenao] [google] >>7138435 Thanks man

>>	Anonymous Thu Mar 19 03:02:44 2015 No.7139625 >>7133383 When Zoloft says no alcohol, do they mean "no alcohol ever ever ever," "a non-alcoholic beer is okay (they can have up to .5% abv)," or "a Bud light is okay very sparingly but we can't put that on a medication warning."

>>	Anonymous Thu Mar 19 03:06:30 2015 No.7139631 File: 20 KB, 600x330, article_fecal_transplant.jpg [View same] [iqdb] [saucenao] [google] Fecal transplants. Science or flummery?

>>	Anonymous Thu Mar 19 03:19:07 2015 No.7139645 >>7139631 I transplanted my feces long before it became medical

>>	Anonymous Thu Mar 19 04:26:12 2015 No.7139712 >>7139625 They mean drinking alcohol becomes way more fun on Zoloft

>>	Anonymous Thu Mar 19 04:29:10 2015 No.7139713 >>7139712 Cool, thanks.

Anonymous Thu Mar 19 05:49:57 2015 No.7139770

>>7136674
>What's circled in red is what we call
>slopes

Jesus but that is some degree of sad.

At any given point on a line, that line has a slope. The "slope" is the amount the line moves up and/or down when you go to the next spot on the graph.

On your curved line y=f(x), the slope has different values at all points because it keeps changing how much it moves. Compare:

going from f(0) = 2 to f(1) = 2.5 - you moved up 0.5

going from f(1) = 2.5 to f(2) = 2 - you moved down 0.5

HELPFULLY, they have drawn an extra line on your function. That line has a fixed slope for all points.

Since that extra line is a tangent to your function f(x) at f(0), you know the slope of f(x) is the same as that of the straight line at that specific point.

f'(x) is a function that describes the slope of f(x) at all points x. That means f'(0) is the slope of f(x) at x=0, which the tangent line can be used to calculate - if you want to calculate it, the slope of a straight line is found by taking to points on the line (x0,y0) and (x1,y1) and calculating (y1-y0)/(x1-x0).

Picking (0,2) and (1,3), we get (3-2)/(1-0) = 1/1 = 1.

The slope of the line is 1

The slope of f(0) is the slope of the line

f'(0) is the slope of f(0)

f'(0) = 1

To find f'(1), do the same, except this time there is no helpful line for f(1). Still - look at the graph, imagine what the line would look like. What slope would that line have? That's your answer for f'(1).

To find f(0) and f(4), you had best be trolling son.

>>	Anonymous Thu Mar 19 10:26:36 2015 No.7140032 how did this: (2(2i-1))/2i with this: 2/2 become this: (2i-1)/i ?

>>	Anonymous Thu Mar 19 10:29:58 2015 No.7140041 what are some good books on intro to topology and what background do i need to study it thanks

>>	Anonymous Thu Mar 19 11:59:55 2015 No.7140168 >>7140032 two's cancel what the fuck are you trying to ask

>>	Anonymous Thu Mar 19 12:06:54 2015 No.7140177 >>7140041 Munkres Topology That's it

Anonymous Thu Mar 19 12:09:36 2015 No.7140179

Prove that if all normal lines to a connected regular surface meet a fixed straight line, then this surface is a surface of revolution.

Also, once I've studied classical diff geo, stuff like surfaces and curves in 3D, what's a good book to move on to that does an introduction to diff geo on manifolds in R^n?

>>	Anonymous Thu Mar 19 13:44:30 2015 No.7140377 how essential is getting into an REU program to getting into math grad school?

Anonymous Thu Mar 19 14:37:16 2015 No.7140471

Anyone here good at translating Logic into English, I'm having trouble with some from a worksheet, I can do the simple ones but I can't do the latter, I have no idea what:

∀p.∀z.(P(a,p)^A(p,v,z))→P(b,z)

where:

>A(x,y,z): adding vector y to vector x results in vector z

>P(x,z): z is a point on line x

is suppose to be saying in coherent English, I can translate it into a bunch of fragmented statements but not a single one. Been using:

http://www.zweigmedia.com/RealWorld/logic/logic7.html

to try and get a bunch of decent examples that I can check whether or not they're correct but still can't make sense of it?

Anyone able to translate it or provide me some better resources that I can practice with?

Anonymous Thu Mar 19 16:49:54 2015 No.7140701
File: 31 KB, 576x765, 20111228.gif [View same] [iqdb] [saucenao] [google]

>>7140471
For all p and for all z, the point z on line x raised to the power of the result of adding vector y to vector x results in vector z gives you z which is a point on line b.

I'll admit that I've never done this before, so either I've just got that from background knowledge or I'm atop Mount Stupid.

>>	Anonymous Thu Mar 19 17:23:30 2015 No.7140786 >>7140471 For every point on a, the point that results from adding v to a lies on b.

>>	Anonymous Thu Mar 19 17:30:19 2015 No.7140805 >>7140786 *from adding v to this point lies on b.

Anonymous Fri Mar 20 04:17:18 2015 No.7141851

if A, B, C are subsets of a finite set X such that |A| = 30, |B| = 40, |C| = 20, |A U B| = 60, |A U C| = 40, |A ∩ C| = 5, |B ∩ C| = 0, |A ∩ B| = 10, how do i find |A U B U C|? so far i've got 30 + 40 + 20 - 5 - 10 but i can't figure out how to get |A ∩ B ∩ C|

i know the answer is 75

>>	Anonymous Fri Mar 20 04:32:44 2015 No.7141872 >>7141851 ahhh i just drew a venn diagram of it and i assume since \|B ∩ C\| = 0 you dont have to worry about \|A ∩ B ∩ C\| since there is never a trisection

>>	Anonymous Fri Mar 20 07:14:37 2015 No.7142130 File: 92 KB, 1001x413, sketch-1426849718671.jpg [View same] [iqdb] [saucenao] [google] for C, shouldn't it be 2! S(7,2) and not 3! S(7,2)? if exactly 1 person misses out out then K goes from 3 to 2, so K! should be 2! and not 3!

Anonymous Fri Mar 20 07:37:10 2015 No.7142160

>>7142130
i think i understand the reasoning. if anyone can proof with this that'd be greatly appreciated (im just going through a large set of problems writing how i interpret and answer them)

>c. slighty different reasoning (to B). There are still 3 people (|K| - 3), 1 person just gets none so the partition (K in S(N, K)) is changed, but the number of surjective functions (3!) stays the same

Anonymous Fri Mar 20 07:48:53 2015 No.7142171

>>7142130
what is S(7,3)=301 ?

think about this
how many ways can exactly two people miss out?
there are only 3 ways exactly two people miss out
there are only 3 ways a single person takes all the packages

so 3+c := at least one person misses out
we must have 3+c+b=a
I don't know about the answer to b

>>	Anonymous Fri Mar 20 07:52:09 2015 No.7142177 >>7142171 S(7,3) is the stirling number for n = 7, k = 3

>>	Anonymous Fri Mar 20 07:57:30 2015 No.7142182 >>7142130 pick one person who will certainly miss out distribute 7 packages among the remaining two in two of those circumstances, one of them will not get anything we can choose the person who misses out in 3 different ways 3*( 2^7 - 2 ) = 378

Anonymous Fri Mar 20 08:01:29 2015 No.7142185

>>7142182
>we can choose the person who misses out in 3 different ways

understood everything up until here. what do you mean we can choose the person who misses out in 3 different ways? as im typing this i think i understand what you mean, do you mean A can miss out, or B can miss out, or C can miss out? hence 3 different ways? i think we're expected to use the formula K!S(N,K) to find the total number of surjective functions of f: N -> K

>>	Anonymous Fri Mar 20 08:07:38 2015 No.7142189 >>7134427 >else why do people do that? if T=0, exp(-α*T)=1. you don't have to use different branches

>>	Anonymous Fri Mar 20 08:11:14 2015 No.7142192 >>7134555 none of these is correct, the potential lines cannot cross

Anonymous Fri Mar 20 08:38:13 2015 No.7142223

>>7142185
I have no idea about the sterling method, or whatever is supposed to be the formal way of solving these types of questions
but I do think my solution is correct

>we can choose the person who misses out in 3 different ways
yes, if we pick A, ie A will certainly miss out, we can distribute the 7 package among B and C. But in 2 of those 128 cases, either B or C gets nothing, we don't want to count those.
So you need to manipulate those sterlings to get 378 and make sense out of it

>>	Anonymous Fri Mar 20 08:39:13 2015 No.7142224 >>7142192 this is a joke right? that is clearly because he drew it in paint.

>>	Anonymous Fri Mar 20 08:42:45 2015 No.7142226 what's the background i need to study topology

>>	Anonymous Fri Mar 20 08:45:25 2015 No.7142230 >>7142226 Yotsuba B is the default

>>	Anonymous Fri Mar 20 08:52:19 2015 No.7142236 File: 893 KB, 2035x1913, DSC_0016.jpg [View same] [iqdb] [saucenao] [google] could someone explain to me why a-d are ordered but e-h are unordered?

>>	Anonymous Fri Mar 20 08:55:26 2015 No.7142242 >>7142230 what

>>	Anonymous Fri Mar 20 08:58:22 2015 No.7142246 >>7142236 if they are unique, it matters if someone gets the first package or the 7th package if they are the same package, only the amount of packages matter

>>	Anonymous Fri Mar 20 11:56:31 2015 No.7142467 Hey, I have a hard time calculating stuff like z^3=1 How do I understand what needs to be done?

>>	Anonymous Fri Mar 20 12:09:42 2015 No.7142483 >>7142467 you have to think polar coordinates are you familiar with them? cis(theta) or e^(i*theta)

>>	Anonymous Fri Mar 20 12:25:09 2015 No.7142502 >>7142467 Don't use exponential notation of complex numbers like the guy above tried to say for exponents as low as 3. Either z^3-1^3=0 Or just let z=x+yi

>>	Anonymous Fri Mar 20 12:27:22 2015 No.7142504 File: 20 KB, 300x294, IMG_20150220_165022.jpg [View same] [iqdb] [saucenao] [google] Why does the inner cylinder(blue)rotate around it's central axis assuming the lube(yellow) is perfect?

>>	Anonymous Fri Mar 20 12:35:20 2015 No.7142510 >>7142504 How do you know it does?

Anonymous Fri Mar 20 12:37:03 2015 No.7142513

>>7142502
what the hell are you talking about
how the fuck are you supposed to find 1/2*(-1+sqrt3i) from z^3-1^3=0
i found that answer in literally 2 seconds

even for square roots, use exponential notation
rectangular notation is not good for anything other than addition/subtraction

>>	Anonymous Fri Mar 20 12:37:10 2015 No.7142514 >>7136584 Then there is Greece where we do double integrals(without the geometrical interpretation), cauchy-schwarz integral inequality and integral mean value theorem in high school.

Anonymous Fri Mar 20 12:45:51 2015 No.7142520 [DELETED]

>>7142510
Well, prof said it does. It's assumed we have fluid dynamics and rigid body mechanics knowledge but I lack the former. By my rigid body mechanicks knowledge, the outer cylinder would roll while the inner would just move parallel to the ground.

>>	Anonymous Fri Mar 20 12:48:45 2015 No.7142525 >>7142513 You're supposed to use an identity which isn't that long. Why are we even arguing what's the fastest way to solve a highschool problem where either way is less than 15 seconds?

>>	Anonymous Fri Mar 20 12:52:59 2015 No.7142532 >>7142520 I don't think a perfect lube is supposed to have any effect other than make shit frictionless, so that leaves the air.

>>	Anonymous Fri Mar 20 12:55:35 2015 No.7142534 Let's say i'm traveling the universe with my spacecraft and at some point i reach the "edge" of the universe or "border". What happens if i try to go further?

>>	Anonymous Fri Mar 20 13:02:27 2015 No.7142546 >>7142525 there is no way you can solve z^3-1^3=0 by putting z=x+yi in 15 seconds

>>	Anonymous Fri Mar 20 13:03:28 2015 No.7142550 >>7142534 edge expands faster than the speed of light, you'll never catch up also, no one knows what is beyond the edge of the universe

>>	Anonymous Fri Mar 20 13:13:13 2015 No.7142565 How do I determine how much energy(KWh) is output by an antenna?

>>	Anonymous Fri Mar 20 15:49:38 2015 No.7142823 >>7142532 What does the air have to do with this? the inner cylinder experiences no drag. The outer one, assuming the air is evenly distributed, won't rotate any faster.

Anonymous Fri Mar 20 15:54:28 2015 No.7142835

>>7142823
The outer one would make the air rotate and the inner one would experience drag from this and rotate as well. I mean yea it's far-fetched and the effect would be negligible but I don't see how else a cylinder with perfect lube on it's surface is gonna rotate.

Anonymous Fri Mar 20 15:58:07 2015 No.7142839

>>7142504
In a previous thread with this same pic and question someone said
>As the outside cylinder turns, it imparts a shear force on the lube, which then pulls the inner cylinder along causing it to rotate due to the no slip condition on the solid/lube interfaces.
Can anybody explain?

>>	Anonymous Fri Mar 20 16:02:17 2015 No.7142845 >>7142534 You'd find yourself back where you started.

>>	Anonymous Fri Mar 20 16:06:25 2015 No.7142851 >>7142845 but who was start?

>>	Anonymous Fri Mar 20 18:12:43 2015 No.7143110 What textbooks for calculus self-study would /sci/ recommend?

>>	Anonymous Fri Mar 20 18:15:23 2015 No.7143115 >>7143110 http://4chan-science.wikia.com/wiki/Math_Textbook_Recommendations

>>	Anonymous Fri Mar 20 18:33:02 2015 No.7143139 >>7143110 you should know that spivak is a shit book unless you are a math major

>>	Anonymous Fri Mar 20 18:40:06 2015 No.7143152 >>7143139 Spivak's easy. Did you mean Rudin?

>>	Anonymous Fri Mar 20 18:59:24 2015 No.7143187 >>7143152 Spivak is better in every single aspect.

>>	Anonymous Fri Mar 20 19:02:22 2015 No.7143197 >>7143115 >>7143139 >>7143152 >>7143187 dont use spivak if youre gonna be physicist or engineer

>>	Anonymous Fri Mar 20 19:05:13 2015 No.7143204 >>7143197 Self studying so whatever. Already have a medical degree.

>>	Anonymous Fri Mar 20 19:06:34 2015 No.7143209 >>7143187 Pretty sure that's what I said. >>7143197 I'm an engineer. Spivak's fun.

>>	Anonymous Fri Mar 20 19:07:07 2015 No.7143212 >>7143204 if you are interested in mathematics itself, it will be a good idea. but if you need calculus for something, something else

>>	Anonymous Fri Mar 20 19:07:54 2015 No.7143214 >>7143197 What's wrong with it for physics and engineering?

>>	Anonymous Sat Mar 21 06:40:55 2015 No.7143995 >soft science Are fetishes born or developed?

>>	Anonymous Sat Mar 21 06:57:46 2015 No.7144007 >>7143995 as a fetishist of multiple things: i think they are developed i wasn't always into tentacle porn and toe sucking

>>	Anonymous Sat Mar 21 07:46:10 2015 No.7144049 easy one for you /sci/ Radicals,Rationals and complex numbers . . . what the hell do I do with them and HOW will I use them? if I understand the why I always learn a lot better

>>	Anonymous Sat Mar 21 07:46:14 2015 No.7144050 File: 33 KB, 832x134, sketch-1426938260669.jpg [View same] [iqdb] [saucenao] [google] could someone show me how this question could be reworded to be a permutation instead of a combination? i have a hard time distinguishing between the 2 for questions

Anonymous Sat Mar 21 07:53:27 2015 No.7144052
File: 69 KB, 345x546, Untitled.png [View same] [iqdb] [saucenao] [google]

HSfag here. is it possible to do a masters out of your field after getting ANY bachelors degree? in this regard could i focus on theoretical physics for my grad studies after doing an engineering physics degree? this is the program i want to enroll in. it doesn't allow minors.

>>	Anonymous Sat Mar 21 08:26:58 2015 No.7144074 How much slower will be a bar magnet dropped through an iron tube compared to dropping it through a copper wire? Please explain in autistic detail

Anonymous Sat Mar 21 09:42:48 2015 No.7144160

>>7144074
in real life the magnet will stick to the insides of the iron. it will lose orientation, it will somehow get stuck inside.

If the insides of the tube were frictionless, copper would slow the magnet more, iron would get hotter
i'd bet 5$ on this information, I wouldn't bet 50$

>>	Anonymous Sat Mar 21 09:46:58 2015 No.7144162 >>7144160 what if the iron were perfectly fit inside the tube and without friction

Anonymous Sat Mar 21 09:47:21 2015 No.7144163

>>7144160
the reason is because copper has a lower resistance than iron and the reason the magnet slows down is the current flowing in the tube. The more resistive the tube is, the less effective that current will be. The current in the copper tube will be more effective. Copper will slow down better.

If the tube were a super conductor, it completely stop, the magnet would be suspended midair
which is basically the principle behind "quantum levitation"

>>	Anonymous Sat Mar 21 09:47:59 2015 No.7144164 >>7144162 I mean, the magnet inside the iron tube

>>	Anonymous Sat Mar 21 09:48:22 2015 No.7144166 >>7144162 >what if the iron were perfectly fit inside the tube and without friction i already said: >If the insides of the tube were frictionless, copper would slow the magnet more, iron would get hotter

>>	Anonymous Sat Mar 21 09:53:52 2015 No.7144169 >>7144166 >copper would slow the magnet more, iron would get hotter that doesn't make sense the slower the magnet, the hotter the tube since slowing down the magnet means taking away some of its energy

>>	Anonymous Sat Mar 21 09:56:46 2015 No.7144172 >>7144169 you are correct, the power would be smaller though, it would spend more time in you know what, it is difficult to say without calculating but copper would be slower

>>	Anonymous Sat Mar 21 10:07:00 2015 No.7144179 File: 5 KB, 965x572, dasfafsdgr.png [View same] [iqdb] [saucenao] [google] >>7144172 I think the iron tube would make it slower I'm not sure how to calculate it though,

>>	Anonymous Sat Mar 21 10:10:38 2015 No.7144183 >>7144179 maybe the magnet would stay in place instead of falling

>>	Anonymous Sat Mar 21 10:13:03 2015 No.7144189 >>7144179 have no doubt, copper will be slower it has nothing to do with the magnet pulling the iron

>>	Anonymous Sat Mar 21 10:13:59 2015 No.7144191 >>7142230 Top kek

>>	Anonymous Sat Mar 21 10:23:40 2015 No.7144201 >>7144189 >it has nothing to do with the magnet pulling the iron why not

Anonymous Sat Mar 21 10:31:46 2015 No.7144212

>>7144201
because it will pull downwards as much as upwards
when it is about to enter the iron tube, metal tube will catapult the magnet in, but when it is in the middle it will have no effect
also, when iron is exiting the tube, the energy it gained when it was just entering, will be removed

>>	Anonymous Sat Mar 21 10:38:28 2015 No.7144221 can someone tell how they find/measeure G in newtons law of gravity F=Gm1m2/d^2

>>	Anonymous Sat Mar 21 10:47:04 2015 No.7144229 >>7144221 you need the planet's mass, planet's radius, gravitational acceleration F_grav=m2g=Gm1*m2/d^2

>>	Anonymous Sat Mar 21 10:50:51 2015 No.7144234 >>7144229 that leads me to another question, how the hell do they measure those?

>>	Anonymous Sat Mar 21 10:54:42 2015 No.7144240 >>7144212 can you elaborate with math?

Anonymous Sat Mar 21 11:37:30 2015 No.7144278 [DELETED]

>>7144240
m=0.01;%mass
g=9.8;%gravity
p=1/2;%the power of velocity the magnetic reverse force is proportional to
%eg. for p=2, F_magnetic = k*v^p
v_t=3;%terminal velocity inside the tube
k=m*g/v_t;%constant expressed in F_magnetic = k*v^p

dt=0.0001;%time step
duration=10;
t = 0:dt:duration-dt;
x=zeros(1,duration/dt);
v=zeros(1,duration/dt);
a=zeros(1,duration/dt);
P=zeros(1,duration/dt);
E=zeros(1,duration/dt);
E_t=0; %total energy

a(1)=g;
for s= 2:length(t)
a(s)=k/m*(v_t^p-v(s-1)^p);
v(s)=v(s-1)+a(s)*dt;
x(s)=x(s-1)+v(s-1)*dt;
P(s)=k*v(s)^p*v(s);
E_t=E_t+P(s)*dt;
E(s)=E_t;
end

figure
hold on
subplot(3,2,1)
plot(t,a)
title('acceleration')
subplot(3,2,2)
plot(t,v)
title('velocity')
subplot(3,2,3)
plot(t,x)
title('position')
subplot(3,2,4)
plot(t,P)
title('power')
subplot(3,2,5)
plot(t,E)
title('energy')

>>	Anonymous Sat Mar 21 11:38:35 2015 No.7144280 >>7144240 >>7144278 if you have matlab, you can play with v_t to simulate the effects of iron vs copper, (copper will have a smaller v_t) this does not take into account the initial catapulting effect though

Anonymous Sat Mar 21 12:06:24 2015 No.7144310
File: 8 KB, 496x398, ScreenShot261.png [View same] [iqdb] [saucenao] [google]

>>7144280
this is a better code
play with the values if you have matlab

an example outcome of an experiment with a material that permits terminal velocity of 4m/s and if magnetic force were equal to f=k*v^(3/2)

>>	Anonymous Sat Mar 21 12:06:48 2015 No.7144314 >>7144234 >>7144229 Actually Big G was first measured by using a torsion spring.

>>	Anonymous Sat Mar 21 12:07:24 2015 No.7144315 >>7144310 http://pastebin.com/wPnKbrbg

Anonymous Sat Mar 21 12:11:14 2015 No.7144321
File: 1004 B, 128x44, 93c2ad88db58f9a86e499b231340a65c.png [View same] [iqdb] [saucenao] [google]

>>7144280
>>7144310
>>7144314
turns out, Force is indeed linear wrt velocity
https://en.wikipedia.org/wiki/Lorentz_force_velocimetry#Principle_and_physical_interpretation

Anonymous Sat Mar 21 13:29:19 2015 No.7144429
File: 26 KB, 553x606, mean....png [View same] [iqdb] [saucenao] [google]

>>7133383
Can someone explain pic related to me? I can tell that what they want you to do is count the squares, but why does this give you the MEAN force?

Also, is there anyway to use calculus on this? I'm sick of fucking counting these squares.

>>	Anonymous Sat Mar 21 14:00:00 2015 No.7144467 File: 34 KB, 553x606, 1426958959524.png [View same] [iqdb] [saucenao] [google] >>7144429

>>	Anonymous Sat Mar 21 15:02:15 2015 No.7144579 >>7144467 I suppose that works, but I'd like a more exact method. Can you help me with why this is the mean impulse?

>>	Anonymous Sat Mar 21 15:06:20 2015 No.7144588 >>7144579 >exact method there is no exact method someone squiggled a line, thats it is this a graded homework, i'd wager the area of my triangle would be as accurate as counting the boxes

>>	Anonymous Sat Mar 21 15:08:56 2015 No.7144594 >>7144588 Fair enough, it's just some stuff I grabbed online. My biggest problem is why this is the mean impulse rather than anything else.

>>	Anonymous Sat Mar 21 15:10:45 2015 No.7144599 >>7144594 >why this is the mean impulse >this what is this? your graph is the exact F(t) graph, its integral is impulse, you want the area

>>	Anonymous Sat Mar 21 15:13:30 2015 No.7144602 >>7144599 I understand that it will be an impulse, but why the mean impulse?

>>	Anonymous Sat Mar 21 15:15:06 2015 No.7144607 >>7144602 >mean impulse what the actual fuck are you talking about

Anonymous Sat Mar 21 15:18:07 2015 No.7144613

>>7144607
Holy shit I'm retarded.

Fuck you dyslexia, fuck you.

Though that being said, I even find the mean force thing a bit weird, I was under the impression that impulse at a given time=force applied at give time * time. Where does the mean force come in?

>>	Anonymous Sat Mar 21 15:19:21 2015 No.7144615 >>7144613 Wait... the time is the total time of contact, not just some given time. I CAN FEEL THE RETARD LEAVING MY BRAIN!

Anonymous Sat Mar 21 15:23:27 2015 No.7144624
File: 40 KB, 553x606, 1426958959524.png [View same] [iqdb] [saucenao] [google]

>>7144613
this is why one should never respond to highschool questions

there is no mean force
mean force would be a horizontal line cutting the area in half
I just eyeballed the red lines so that it'd be easier to calculate
with each segment, i tried to have equal amounts of extra area included and area not include

>>	Anonymous Sat Mar 21 15:27:25 2015 No.7144627 >>7144624 Fair enough, looks like I can't brain today. Is this really high-school level in your country? In mine it's last year of college, most people who sit it would've only just turned 18.

Anonymous Sat Mar 21 16:02:38 2015 No.7144698
File: 7 KB, 553x383, Circle.png [View same] [iqdb] [saucenao] [google]

>>7133383
This one's annoying me. Consider an object moving in uniform circular motion. The only forces acting on it are it's weight and the normal contact force.

What's confusing me are the points B and D, how is there any normal contact force at these points?

I strongly suspect that my confusion comes from misunderstanding the normal contact force, so feel free to break it down to the most pleb level you can.

Anonymous Sat Mar 21 16:08:48 2015 No.7144711

>>7144698
I suppose that I can put this better than I did...

At C, I can clearly see that as the object is exerting the force of its weight on the container, the container will exert an equal and opposite force on the object, this force is known as the normal contact force, I can easily see the same argument being applied to any other points except for A, B and D.

At A, I can't see how the object can exert any force on the container, so I most argue that the normal contact force is zero. Fortunartly, as the weight is acting towards the centre of the circle, circular motion is conserved.

At B and D however, the force of the weight isn't in line with the container, so I fail to see how there can be any normal contact force, however if that was true, the net force wouldn't be directed towards the centre of the circle (as the only two forces are the weight {acting down} and the normal contact force of magnitude 0), so how could we have circular motion?

Anonymous Sat Mar 21 16:11:27 2015 No.7144722

>>7144698
does the gravity pull objects from A to C, is that diagram vertical?
if so, it cannot be "uniform" circular motion, its speed will change
imagine the object just before it is at D, its velocity will have some leftwards component, but there no is place to go on the left, so that velocity will turn into force

Anonymous Sat Mar 21 16:12:51 2015 No.7144726

>>7144711
>At C, I can clearly see that as the object is exerting the force of its weight on the container, the container will exert an equal and opposite force on the object, this force is known as the normal contact force, I can easily see the same argument being applied to any other points except for A, B and D.
>At A, I can't see how the object can exert any force on the container, so I most argue that the normal contact force is zero. Fortunartly, as the weight is acting towards the centre of the circle, circular motion is conserved.
you have no understanding of circular motion
you need to work on examples of ACTUALLY uniform circular motion without the effects of gravity and understand that before you try to understand nonuniform circular motion

>>	Anonymous Sat Mar 21 16:17:26 2015 No.7144736 >>7144722 Yeah it's vertical, though I can't understand your D argument. For practicality's sake we'll say it's moving clockwise. >>7144726 >you have no understanding of circular motion How so?

>>	Anonymous Sat Mar 21 16:22:52 2015 No.7144752 >>7133485 >physics and philosophy KeK

>>	Anonymous Sat Mar 21 16:24:39 2015 No.7144755 >>7133945 Calculus would not be a thing

>>	Anonymous Sat Mar 21 16:26:55 2015 No.7144761 >>7134129 Agreed

>>	Anonymous Sat Mar 21 16:27:24 2015 No.7144762 >>7144736 >>you have no understanding of circular motion >How so? you simply don't if you need to understand it, you will need more than what someone can explain in a post

>>	Anonymous Sat Mar 21 16:28:32 2015 No.7144764 >>7134375 Get kinky

Anonymous Sat Mar 21 16:28:59 2015 No.7144766

>>7144711
>At C, I can clearly see that as the object is exerting the force of its weight on the container, the container will exert an equal and opposite force on the object, this force is known as the normal contact force, I can easily see the same argument being applied to any other points except for A, B and D.
>At A, I can't see how the object can exert any force on the container, so I most argue that the normal contact force is zero. Fortunartly, as the weight is acting towards the centre of the circle, circular motion is conserved.
kek, this is what happens when people try to explain circular motion with centripetal force rather than centrifugal force

Anonymous Sat Mar 21 16:32:25 2015 No.7144771
File: 24 KB, 652x565, Self-redemption.png [View same] [iqdb] [saucenao] [google]

>>7144766
Well, if it counts for anything, here's the question that sparked all this off, maybe I'm not seeing something. All I tried to do was argue that the net force must always be directed towards the centre of the circle.

Anonymous Sat Mar 21 16:34:19 2015 No.7144778

>>7144698
After it passes C it will start accelerating towards B due to the contact force.
At D it's moving up and still accelerating towards B. Gravity isn't in the correct direction to be accelerating it towards A. If there was no contact force at D it would just keep going up until gravity stopped it. Think of a half-pipe

>>	Anonymous Sat Mar 21 16:38:50 2015 No.7144793 File: 1.52 MB, 300x224, 1426493071203.gif [View same] [iqdb] [saucenao] [google] >>7144771 do your own homework

Anonymous Sat Mar 21 16:39:35 2015 No.7144797

>>7144778
While I totally agree with you, I fail to see how there can be a contact force at D. To the best of my knowledge, there can only be a contact force at D if the object is exerting a force on the container at D, but it clearly isn't (it's weight isn't acting towards D).

>>	Anonymous Sat Mar 21 16:40:35 2015 No.7144801 >>7144793 I've done it, I'm confused about something that the question isn't asking for...

Anonymous Sat Mar 21 17:13:24 2015 No.7144912
File: 173 KB, 850x672, 1383070532396.jpg [View same] [iqdb] [saucenao] [google]

>>7144797
Now I'm confused too

>there can only be a contact force at D if the object is exerting a force on the container at D
The container is exerting the contact force on the object.
If you push a car, the contact force is between you and the car. Just because the car isn't going in reverse or may theoretically not have friction doesn't mean you don't experience the resisting contact force as well.

>>	Anonymous Sat Mar 21 17:20:49 2015 No.7144944 >>7144912 >If you push a car Newton's Third Law, bitches. You've exerted a force on the car, so it's exerted a force on you, the same cannot be said of >>7144797

>>	Anonymous Sat Mar 21 17:25:27 2015 No.7144957 >>7144944 The container is pushing the sock towards its center. The fact that there's no force pushing the sock towards the container doesn't mean that it can't receive a contact force.

>>	Anonymous Sat Mar 21 17:26:42 2015 No.7144960 >>7144957 If the contact force isn't a result of Newton's third law, then what is it?

Anonymous Sat Mar 21 17:32:35 2015 No.7144983

>>7144960
>container is pushing the sock towards its center.
3rd law just says that the container is also being pushed.
It's intuitive; if the container didn't have a way to counter its contact force then it would mean the axis (axle?) broke and it would be pushed away toward whatever direction the sock is relative to the center of mass.

>>	Anonymous Sat Mar 21 17:34:58 2015 No.7144987 >>7144983 What contact force? I don't see how the container is relevant.

>>	Anonymous Sat Mar 21 17:39:32 2015 No.7144992 >>7144987 The container is the thing exerting force on the object.

Anonymous Sat Mar 21 17:46:12 2015 No.7145011

>>7144992
...I think I can work with that

The sock is in circular motion.
Therefore the resultant of the weight, contact force and whatever force the container is exerting is directed towards the centre of the circle...

If only I knew something about the force the container is exerting, mind explaining it to me?

>>	Anonymous Sat Mar 21 18:06:15 2015 No.7145066 >>7136559 I took calculus in 11th grade...

Anonymous Sat Mar 21 18:09:17 2015 No.7145073
File: 9 KB, 445x338, f.png [View same] [iqdb] [saucenao] [google]

>>7145011
>The sock is in circular motion.
>Therefore the resultant of the weight, contact force and whatever force the container is exerting is directed towards the centre of the circle...
It's not in uniform circular motion; just the projection onto the normal vector is towards the center. I think.

>contact force and whatever force the container is exerting
Same.

Clearly you can see that the sock will be moving slower at the top of the container than at the bottom.

Here's a badly drawn diagram.

>>	Anonymous Sat Mar 21 18:19:09 2015 No.7145110 >>7140032 what do you mean by "with this" What the fuck are you talking about, use words with precise definitions Also the final expression is just a simplification of the first expression, its fucking introductory level algebra

Anonymous Sat Mar 21 18:29:16 2015 No.7145134

>>7144052
I don't know specifically for your field, but there are plenty of people who go into different grad school fields than what they did as undergraduate. You just have to demonstrate that you have a good enough grasp on that field before you get accepted into the program.

>>	Anonymous Sat Mar 21 18:37:42 2015 No.7145157 >>7144052 just do electrical engineering or cs, man

Anonymous Sat Mar 21 21:30:08 2015 No.7145508
File: 59 KB, 715x955, Untitled.jpg [View same] [iqdb] [saucenao] [google]

>asking for homework help
Please excuse my inability for such a low level question and requesting this.

I'm doing an assignment and working on a question that's similar to the example pictured. I'm confused about the two red boxes; I believe they contain the same thing, that being the second derivative of r(t), yet the answer for each is different. Why is this?

If required, the assignment question I'm working on uses
r(t) = <sin(t), 2cos(t)>

I can provide more information or clearer pictures if also required.

>>	Anonymous Sat Mar 21 23:24:14 2015 No.7145658 >>7144771 ...anyone figured this out yet? It's took my entire day, hopefully I'll wake up with an idea.

>>	Anonymous Sun Mar 22 00:19:53 2015 No.7145736 I need to split f(x,y) = 2x^3 + 4y^2 - 12xy into it's components to find the critical points on a graph. How do I differentiate by parts, I cant find any guides on how to split 12xy

>>	Anonymous Sun Mar 22 00:47:38 2015 No.7145775 >>7145508 the first one is derivative of position (vector) and the second is derivative of speed (scalar)

>>	Anonymous Sun Mar 22 01:13:06 2015 No.7145822 Why do vdW forces result in a net attraction? Shouldn't fluctuating dipoles result in repulsion equally often?

>>	Anonymous Sun Mar 22 01:25:36 2015 No.7145836 What's the difference between dx and delta x? How are they used differently?

>>	Anonymous Sun Mar 22 01:26:14 2015 No.7145838 >>7145775 Thank you, Why do they give a different result, is it because the first one represents the position at a fixed value of t while the second is the speed at any given value of t?

Anonymous Sun Mar 22 01:29:56 2015 No.7145847

>>7145836
delta x refers to an average i.e. delta x over delta t is average speed but it's not necessarily how fast you were going at each point in the whole trip. d/dt is a functional operator which if you took dx/dt it takes your function of x and gives you a new function of x which tells you exactly how fast you were going at every x

>>	Anonymous Sun Mar 22 01:31:09 2015 No.7145849 >>7145838 yes because the second is expressed for arc length of your curve. your curve has a distance in m so going distance 10m on your curve is different from displacing position 10m

>>	Anonymous Sun Mar 22 01:32:39 2015 No.7145852 >>7145847 >d/dt is a functional operator which if you took dx/dt it takes your function of x and gives you a new function of x which tells you exactly how fast you were going at every x can you give an example

Anonymous Sun Mar 22 01:38:41 2015 No.7145864

>>7145852
ok say u a position x based on time,
x = t
if at time 0 i'm at x = 0 and time 5 i'm at x = 5
then delta x / delta t = 5 / 5 = 1
this is the average speed for the trip
then if i take dx/dt the new function is dx/dt = 1 so my speed at any point is 1
a better example may be
if my function of time for position x = t^2 then for t = 0 then x = 0 and t = 5 then x = 25
using deltas you can find delta x / delta t = 25 / 5 = 5 so average speed was 5
but if you took dx/dt you obtain dx/dt = 2t so speed at any time t = 2t
i.e. speed at t = 0 = 0
and speed at time 5 = 10, etc

>>	Anonymous Sun Mar 22 01:40:32 2015 No.7145867 >>7145864 thanks I get it now

>>	Anonymous Sun Mar 22 01:44:33 2015 No.7145869 >>7145867 yeah sorry my first time i should have said function of t but anyway it's all about instantaneous

>>	Anonymous Sun Mar 22 03:09:43 2015 No.7145989 File: 164 KB, 995x1085, Capture.jpg [View same] [iqdb] [saucenao] [google] how are they getting this figure of 2? this is really puzzling me and stopping me from actually getting started on the program

>>	Anonymous Sun Mar 22 03:32:08 2015 No.7146022 >>7145989 please respond

>>	Anonymous Sun Mar 22 03:34:52 2015 No.7146026 >>7133999 I'm not sure what Paul's notes are, but in the US we usually split Calc into 3 trimesters, first is derivatives, second is integrals, third is multivariate.

Anonymous Sun Mar 22 03:41:17 2015 No.7146034

Can the force created by kinetic friction ever reach a maximum?
I'm very confused about what happens when a rough object is placed on top of another rough object which is moving at constant velocity.
Surely it can't pass the velocity of the object it is on top of, but my intuition has proved wrong in some cases.

>>	Anonymous Sun Mar 22 03:45:45 2015 No.7146040 >>7145989 >>7146022 figured it out

>>	Anonymous Sun Mar 22 04:15:28 2015 No.7146059 How do you denote a vector in analytic geometry? <span class="math">\bar{u}[/spoiler] or <span class="math">\underline{v}[/spoiler]?

>>	Anonymous Sun Mar 22 05:19:49 2015 No.7146102 >>7146059 in electromagnetism I put a bar on top

Anonymous Sun Mar 22 06:42:31 2015 No.7146172

>>7137482
when x = 0 f'(x) = 0
if you want to see this in terms of the polynomial ignore e^-x because e^0 = 1 and divide it by x-3 or x+3 (those values plugged into the polynomial give 0 therefore divisible)

>>7137643
no light always travels at speed c. see (http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/mmhist.html))

>>7144050
uhhhhhhhh just visualise it or write it down
if you have 15 flavours and need to fit 10 in a bag you would have initially a choice of all 15 flavours for your 10 flavours and (15-n) for every n choice after it. so it would be 15!/(15-10)! (15*14*13 to (15-10)) for b it's just 15^10 (15*15...)

Anonymous Sun Mar 22 06:50:41 2015 No.7146180

>>7146034
no it can't

either friction is high meaning it will just "stick" to the object on the bottom and move with the same velocity or slide off the back assuming friction is minimal and a force such as drag force acts on it in the opposite direction of the

>>	Anonymous Sun Mar 22 11:58:51 2015 No.7146518 >>7145736 Product rule.

Anonymous Sun Mar 22 12:34:06 2015 No.7146569

>>7145736
I see no reason why you would need to "split" that function
you just partially differentiate it to find
(6x^2-12y,8y-12x)
the points where this is (0,0) are critical points
it is more difficult to determine if maximum minimum or saddle point
I know how to do it using hessian matrix but there was an easier way for 2D functions, they should have taught you about it

Anonymous Sun Mar 22 13:28:09 2015 No.7146659

>>7144722
Shit... I finally understand what this guy was saying.

Consider the motion of the object just before D (or the unlabled point from the actual question >>7144771).

Because it's moving in a circle, we know that the centripetal force will be directed towards the centre of the circle.

However, since it's moving in a circle, we know that the velocity is at a right angle to the centripetal force, obviously this velocity has a component directed towards the container.

It follows that the object is trying to move into the container, therefore there must be a normal contact force.

My only issue is then the points where the velocity only has a vertical component (B and D). I'll read over the rest of the posts and see what's been said, am I finally on the right lines?

Anonymous Sun Mar 22 13:42:08 2015 No.7146686

>>7146659
Oh for fuck sake, back to actual question >>7144771.

At all points, the sum of the contact force (R) and the weight (W) will be the centripetal force (C), which I'll assume to be constant.

At A, R+W=C, however R must equal 0 because I see not way that there can be a normal contact force at A (the sock isn't moving towards the container at this point).

At B, I haven't got a fucking clue, R must equal 0 because I see not way that there can be a normal contact force at B (the sock isn't moving towards the container at this point), however the weight is at a right angle to the centripetal force, so it's irrelevant, somehow 0+0=C, which is bullshit.

It follows that I cannot assume that the centripetal force is constant, therefore it's beyond the scope of my course.

Therefore all that remains to satisfy is my own curiosity as I've already answered the actual question.

What the fuck is happening at B?

>>	Anonymous Sun Mar 22 13:45:18 2015 No.7146689 >>7146686 Oh, and am I right to say that there's no contact force at A?

>>	Anonymous Sun Mar 22 15:28:12 2015 No.7146930 >>7146518 >>7146569 Thanks guys. There's probably a way that I've missed, I'll have to check if I'm missing a handout or something.

>>	Anonymous Sun Mar 22 15:44:19 2015 No.7146977 >>7146930 http://www.analyzemath.com/calculus/multivariable/maxima_minima.html exactly what you need for 2D functions you need to memorize the first part

>>	Anonymous Sun Mar 22 16:33:54 2015 No.7147108 >>7146977 Thanks man, followed that and it worked.

Anonymous Sun Mar 22 16:52:03 2015 No.7147153

>>7147108
alternatively, if you have a calculator or a way of evaluating numerically, after you have found the points where (Fx,Fy)=(0,0)
say it is the point (a,b)
you can evaluate the function at
(a+0.001,b)
(a+0.001,b+0.001)
(a+,b+0.001)
(a-0.001,b+0.001)
(a-0.001,b)
(a-0.001,b-0.001)
(a,b-0.001)
(a+0.001,b-0.001)
(surround the point from 8 sides basically, maybe 5 sides will be enough, I don't know, but I'd do 8 to be sure)
if all of them are greater than F(a,b) then it is a min, if some bigger some smaller a saddle point and so on

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/sci/ - Science & Math