Stupid Questions Thread I'll Begin. Pic related is the

>take Physics I at a community college
>realize I am terrible at lab
>Lab worth 30% of grade
>Three test worth 40% of grade
>pre-lecture/lab quizzes worth 10% of grade
>homework worth 10% of grade
>Final exam worth 10% of grade

I just started the class, but assuming I do completely terrible on the lab portion of Physics, can I still pass the Physics class if I average 70% on the test?

Does time actually exist? Or is it just a construct of the mind?

>>8130395
Depends on how terrible is terrible.

Just add up like .7 * .4 for your 70% on the tests, .8 * .1 assuming you get 80% on the quizzes, .9 * .1 assuming you get 90% on the homeworks, etc all the way down except for the labs, then subtract from .7 (or whatever overall percentage you want in the class) and divide by .3 and you have the percentage you need to get on your labs in order to get that grade.

>>8130395
labs, prelecture, and homework having such high percentages are to HELP your grade

As long as you're completing the lab tasks, at least attempting to show a conscious thought process in your lab report, and do the prelectures/homework you should do just fine.

The goal of all that supplementary stuff is to try and make sure everyone is exposed to the concepts/problem solving techniques as much as possible before being tested on it.

>>8130633
Remember that physics, especially fundamental physics, is a model/a conceptual framework for understanding the universe and its processes moreso than a description/some divine elucidation.

A time dimension comes into physical models spanning from fundamental/sub-atomic to standard mechanics to general relativity and greater cosmologies. The notion of time as separate from the spatial dimensions isn't quite right (i.e. Lorentz boosts are fundamental flat spacetime transformations), but it's also a bit off-target to go and say they're the same thing/we live in 4 spatial dimensions (Euclidean time/Wick rotations are useful calculational tricks--even in wacky coordinates the metric signature isn't changed).

>>8129493
Please help

>>8130395
Exams are worth 100 % here, always. It's not good because you cannot make exams comprehensive enough to test everything, so your performance will vary regardless of how well you prepared. This might also people to make it through exams just barely only to utterly fail in many other ones because they estimated the necessary preparation (wrongly) on their previous performance. Furthermore, you might do all your homework (takes much time and also quite some effort) or you might just learn exam questions (takes less time and definity similar or less effort). What do you think is a better strategy to understand your material?

Realistically, with future medical and technological advancement, how long should someone currently in their 20s expect to live?
Are we even close to understanding neural networking to the point of being able to transplant a human brain into say a robot body or a virtual reality? thus achieving a greatly extended life?

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Alright I'm starting out with Electronics and can't wrap my head around this problem. I know it's pretty much EE 101 but still would appreciate some help.
I need to calculate the I from this circuit, all the resistances are in Ohms of course. Only the U on R2 is known and it's 15 V.

What I would do is:

Take Rw with R1 as paralell and then add to R2 as serial or something.

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>>8129493
>Pic related is the Cayley Table dihedral group
> This doesn't look like any Cayley table I've ever seen
then how the fuck do you know that it is a cayley table?
where did you get it from? what kind of shitsource has a picture like that without a detailed legend to explain the symbols being used?

you might as well ask how to differentiate an upside down questionmark that has a squiggly line beneath it, fucktard

pic related, its a cayley table of the dihedral group of 8 elements. notice the element with the big order, thats the rotation

>>8131363
https://en.m.wikipedia.org/wiki/Center_(group_theory)

>>8131321
Rw and R1 are not in parallel.
Can you tell when two components are in series or parallel?

Introduce a current I1 in the branch of R1 and I2 in the branch of R2, try to express them.
How does I relate to I1 and I2?

>>8131384
Alright I think I got it now. the I divides into I1 and I2 going to R1 and R2 respectively.
So if U on R2 is equal to 15V then by U = I * R, I1 * 100 = 15 and I2 * 60 = 15.
Then I do I1 + I2 = I and that gives me 0,4 A.

Did I get it right? I assumed the voltage is equal on R1 and R2 since they are paralell.

>>8131390
looks right to me.

Try to keep everything in terms of given values without replacing.
Something like I1 = U/R1, I2=U/R2
I = U*(1/R1 + 1/R2).

This allows you to check for homogeneity in terms of dimensions.
Once you're sure, you can replace with the given values.
Nobody wants to see you write 1 + R + R^2 + ...

>>8131383
wow, you must have a very good understanding of group theory.
For prior to you posting that link to the English wikipedia article on the center of a group, I had no notion of the center of a group, semi-group/noncommutative ring or algebra.

It is only after you posting that link without context that I understand and regret embarassing myself earlier with that post, exhibiting that indeed I was ignorant of what the center of a non-commutative algebraic object with a multiplication was.

However, after educating myself on the matter, one slight little question remains unresolved, and I hope you might shed some light on the matter by elucidating what in the name of FUCK the center of a group has to do with fucking ANYTHING, ever.

Regards, your mother was a whore

>>8131403
Thanks!

>>8131409
That's where I found the image wise ass. You asked where I found the image and how I knew it was the Cayley table of the dihedral group of 8 elements. Now fuck off unless you actually have something to contribute.

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How come I can't insert the radius of 6.37x10^6m into the circumference equation of 2rpi then convert the answer to km? my 10^ are a few numbers off. Only way to get the right answer is to first convert the meters to km then plug into the equation.

>>8131478
>How come I can't insert the radius of 6.37x10^6m into the circumference equation of 2rpi then convert the answer to km?
but you can

>>8131497

I did. I did not get the same answer as the back of the book. For part B I get 5.10x10^11km^2 instead of 5.10x10^8km^2.

>>8131522
You will find it is not uncommon for the answers in the back of the book to occasionally be incorrect

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I am really dumb so can anybody explain me how did he solve for M in this equation?

>>8131531

The answer on the back of the book is correct if I first convert 6.37x10^6m to km.

>>8131538
Use order of operations and multiply both sides by M to get to the second step, then cube root both sides, isolate M. Its messy but pretty straight forward

>>8131522
you said for the first one.

1km^2 is not 1000m^2, it's 1000 000 m^2.
1km^3 is not 1000m^3, it's 10^9 m^3
this is literally the point of the exercise.

Why can there be no analytic functions with uncountable zeros or poles? I guess an uncountable set of poles would be more of an essential singularity?

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>>8131562

so I was suppose to do this? Damn, there was a similar physics lab problem that I had yesterday. Fuck, I am going to do terrible in this class.

>>8129493
Need help with the following exercise.

- Prove a zero-dimensional Noetherian scheme is nonsingular iff it is the union of reduced points.

(Note that the previous exercise was to prove the underlying top. space of every zero-dim. Noetherian scheme is finite, so you can use that.)

I just got admitted to a university. I am taking a class for my major during the summer and I was wondering what would happen if I get an F in the course or a W. Would the university find out and kick me out?

>>8129493
Two are pretty obvious: The dot is the identity, 7 = r^2 (rotating twice)

Since 7 = r^2, it is also pretty obvious that 17 and 22 are either r and r^3; also since they are the only two who have order greater than 2.

Not sure how to find the others, but it should be easy once r and r^3 have been determined. Not sure about the graphs above.

>>8129493
how do I git gud

>>8130395
Physics 1 at a community college? Holy shit, dont fucking do it. Wait till u get to a university to get a real professor vs some dingleberry at highschool part 2

>>8131409
Ow the edge

>>8131430
Best I can come up with is that D4 is a subset of permutations of 4 elements.
The red squares are supposed to be depictions of those permutations.
I don't know why the author of that image decided that permutation of the 1st and 2nd rows and the 3rd and 4th rows correspond to r^2 (or 7 by his notation).

He must have some some method of assigning 0-23 to the 24 permutations of 4 elements.
His method would probably be neat if I knew what he was doing.

Say I know for any [math]\epsilon > 0 [/math] there exists [math]N[/math] such that [math]n \geq N [\math] implies [math]|a_{n+1} -a_n|<\epsilon[/math]. How can I extend this to show cauchy criteria holds?

>>8132554

What's the difference? My professor has a PhD. The professors who are teaching undergrad Physics at a university are just people with Master's or associate PhD holders who are just doing bitch work for the actual Professor.

Hey, i have no idea wether the following statement is true or false and don't know how to show it, i really need to answer it though and would appreciate your input on this.

The set [math]\{A\in M(n,n)|A*=A\}[/math] of the hermetic matrices is a group in relation to the matrice-addition.
true or false?

>>8132791
I'm not familiar with that set but it's pretty straightforward to show if a given structure is a group: check closure, associativity, presence of an identity element, and closure under inverses. Do you know how to do these things in general?

>>8132799
Alright thanks, i've had groups, sets and so on before and probably learned that but that was 2 years ago and i will have to read into it, I also kind of thought there would be something that i overlooked in that statement that would make the answer seem trivial.

>>8132791
Ah and i did a mistake with the * while writing it. [math]\{A\in M(n,n)|A^*=A\}[/math]

>>8132738
It does not. ln(n) satisfies this but is not Cauchy. The right assumption is that (u_k -u_{k-1}) converge

>>8132826
I meant that the series converge*

How do imaginary exponents work?

>>8132844
with a little bit of imagination.

jk
they don't work.

you can only put an "imaginary exponent" inside an exponential.

if a and b are real,
z = exp(a+ib) = exp(a) * exp(ib).
z has a modulus of exp(a), and an argument b.

Anything else is poor mathematics (including i^i and other shit)

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>>8129493
[math] f(x)=3x^2 [/math]
[math] 3a^2=3b^2 [/math]
[math] a^2=b^2 [/math]
[math] a = ±b [/math]
Not one to one
Why does
[math] a^2=b^2 [/math]
come out as
[math] a = ±b [/math]
and not
[math] a = b [/math]?

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How to do this if there are two of the same values.

>>8132918
Because a^2=b^2 implies a^2-b^2=(a-b)(a+b)=0 so a=b or a=-b

>>8132935
isn't the same true if you just switch a with b?

so

a=+-b
+-a=+-b

and therefor also

+-a=+-b

???

>>8132951
-a = +-b is the same thing as a = +-b

>>8132963
Then why is it not one to one if -a and +a both = +-b?

>>8131619
Please answer.

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I had to solve this problem but couldn't do it on time. I must obtain a relation in which the distance is related to the angle. But I had no idea where to start from the projectile motion formulas.

The answer was supposed to be

[eqn]d(\Theta_0)=\frac{v_0^2sin2\Theta_0}{2g}\left \{1+\sqrt{1+\frac{2gh}{v_0^2sin^2\Theta_0}}\right \}[/eqn]

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I guess this would be the best place to ask this.

I have pictures of grains. I want to extract their shape using matlab. The image has quite a bit of noise. After some operations (noise removal, edge selection, bw area open and line dilatation) i get the picture on the right, the grains are pretty much separated but they are still not counted as regions themselves as they are lumps of empty space between small regions.

Any idea on the next step, or a different approach to the problem altogether?

>>8132920
Group the Pi in one side and just go from there.
[math]e=\frac{P_{i}D_{i}}{2f-P_{i}}[/math]
[math]e(2f-P_{i})=P_{i}D_{i}[/math]
[math]2ef-eP_{i}=P_{i}D_{i}[/math]
[math]2ef=P_{i}D_{i}+eP_{i}[/math]
[math]2ef=P_{i}(D_{i}+e)[/math]
[math]\frac{2ef}{D_{i}+e}=P_{i}[/math]

>>8133062
The range is the x distance when y = 0 -- when the projectile hits the ground (there should be two solutions, pick the non-crazy one).

>>8133140

maybe use some hough transformation to detect circles

>>8133140
try morphological opening or closing (can't remember which plugs holes), with a small structuring element.

in your experience, what is the average actual yield for chemical reactions (generally)

and also, what's the closest yield (to a hundred) that you've gotten

>>8133358
100%, strong acid in water

>>8133361
100?, how's that possible, is a rare yield to get?
but what about the average yields?

>>8133370
Depends desu

>>8133376
tell me more

>>8133376
ok, what about precipitationr reactions, what are the average yields then

>>8133376
>>8133382
>>8133385
halp

what does d/dx, dy/dx mean

what would happen if I use acidic water to dissolve sodium carbonate?

>>8133419
d/dx is a differential operator; you applying to a function to get the derivative (of said function).

dy/dx is the derivative of y=f(x). You could also write it as d/dx[y] to show the differential operator is operating in the function y

>>8133464
Uh, you'd get more water?

>>8133479
can being acidic means more H+, right?
but wouldn't the halogens in the air get in there?

>>8133465
I just want to know why its written that way
why d over dx?, does it mean the derivative over the derivative of x
e.g., how do I read it

>>8133508
Read [math]\frac {d}{dx}(f)[/math] as "the derivative of f with respect to "x".

As for why:
1. It's just notation, don't worry about it.
2. Historically, derivatives were thought of as fractions of infinitesimals. [math]\frac {dy}{dx}[/math] was literally a fraction, with dy being the infinitesimal change in y with respect to dx, the infinitesimal change in x.

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>>8129493
>>8132510
>>8132614
Perhaps this will help

>>8133522
I don't understand.
if dy/dx means the derivative of y with respect to x, and y = f(x), so that means that you're taking the derivative of f(x), but d / dx means the derivative of f with respect to f, and f = y, whats going on

and sorry, i have to worry about it. I need to know how things work to have a peace of mind

>>8133537
*the derivate of f with respect to x

>>8131619
>>8133002
Surely this is simplistic to answer?

>>8133540
Basically, if y = f(x), we can write the derivative of y/f(x) as:
dy/dx, d/dx(y), or f'(x).
These are all different notation for the same thing.

>>8133537
>>8133540

if y = f(x) then yes, dy/dx means the derivative of y with respect to x.

But d/dx is notation for the differential operator; it is not the derivative of anything. We get a derivative when we apply it to a function (be it expressed as y or f).

As the other anon said, the notation is remnant of how derivatives were interpreted way back; dy was an infinitely small change in y, and dx was an infinitely small change in x. The ratio of the two was taken to be the instantaneous rate of change. Its stuck around because, in part, it IS intuitive to think of dy/dx as just that.

>>8133568
I think I get it.
d/dx means the derivative of something with respect to x

so dy/dx means f(x+h) - f(x) / x
e.g. dy == f(x+h) - f(x) and d == x
over smaller quantities to finally be the limit

>>8133578
Sort of, but the d/dx is more of a functional piece of notation than it is anything, sort of like a square root or ln for natural log.

Suppose we have a function y = f(x). It could be anything, a polynomial, logarithm, any of the good stuff you're familiar with from highschool algebra.

Just as we can take the square root of both sides of an equation by literally drawing a radical over the LHS and RHS of the equation, or take the log of both sides by writing log(LHS) = log(RHS), we can apply the differential operator to get the derivative.

so if we have y = x^2 + 2

we can take the derivative (i.e. apply the differential operator) to get

dy/dx = d/dx[x^2 + 2] = 2x

In a rigorous sense an operator is a function that maps a set of functions to itself. I dont know much about that sort of stuff so perhaps another anon can help if you want to get deeper.

>>8133587
should say "sort of like a square root symbol" in the very first sentence

I hope this helps and hasn't added further confusion. If you're still stuck just say something an hopefully someone else can explain it better.

>>8133587
It makese perfect sense now.
Are there many properties to derivaties, just like logarithms have properties.

>>8133592
lol oh yes.. numerous

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Will I get fucked in my studies of pure math if I skip the probability and statistics module? My program includes them but they are not required, so some of my friends are skipping them and taking pure math classes instead.

>>8133631
PSTAT is HAM AF nigga

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what's the best calculator for calculus and beyond?


i know it's not pic related

>>8133635
not interested in that career path at all. I am only asking if I need statistics for pure math somewhere along the line (analysis?)

>>8131630
/sci/ help pls

>>8133690
For exams:
Casio 115es plus/991es plus
Casio 991ex classwiz

For homework:
Matlab, Maple, WinPython/Python(x,y) or equivalent

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How do I simplify / arrange the result on the left to get something like the result on the right.

Left is just part of the result, but I just want to know how he arranged the square root etc in the book example.

End of first year physics student (UK) going into second year. Any books I should read to prepare? There isn't a course book list for second year yet

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>>8133690
I don't know, but it's sure not pic related.

>>8133745
[eqn]\sqrt{\frac{9}{2}}=\frac{3}{2^{\frac{1}{2}}} \Rightarrow \frac{\frac{3}{2}}{\sqrt{\frac{9}{2}}}=\frac{2^{\frac{1}{2}}}{2^{1}}=\frac{1}{\sqrt{2}}[/eqn]

>>8133712
can anyone confirm that these are the masterrace options?

pls no samefag

>>8133712
you guys don't like having the graph display huh? why is that?

>>8133781
Guy with the TI 83 SE here. To be fair, I'm really just trashing it because this model is 17 years old, and I imagine newer ones are more intuitive to use, or have a better display.

Not that I've ever used anything else. Been stuck with this family heirloom since high school.

>>8133690
You won't be allowed to use one in exams and you won't need one outside of them. Save your money.

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All you need.

I have 100 trials, in each trial I flip a coin 100 times. This is the same as flipping a coin 10,000 times. What would the distribution of heads and tails most likely look like over all? Say, 50% heads and 50% tails?

>>8133955
most likely yes.

the probability distribution for the number of heads is a binomial distribution with 10000 trials and probability 0.5

>>8133973
And yet if I flip a coin 100 times, I have the same likelihood of getting 100 heads, as I do anything else, like 45 heads and 55 tails.

Please tell me why analytic functions can only have isolated zeros and singularities.

Do undecidable statements still have a truth value? For instance, is the continuum hypothesis true or false even though we can't prove it?

>>8133983
>I have the same likelihood of getting 100 heads, as I do anything else, like 45 heads and 55 tails.
You described that terribly, as you only have the same likelihood for a chosen permutation of 45 heads and 55 tails, not for that result overall.

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Hey guys, I got a question that is for finals revision and normally I'm great with interferometry, but am struggling with this easy question.

Do I just compare the phase difference to optical path length difference and determine the wave number? When wave number is (2n+1)/2 is when there is complete destructive interference, so do I just find at what OPL change corresponds to when the waves cancel out? I assume there is a better way to solve this as spectral width and wavelength are given (lets temporal coherence length).

I can't find any material on this that concisely answers my concerns and don't have time to ask my professor as the exam is tomorrow morning. If anyone can help me out I will suck your dick.

>>8133996
>analytic functions can only have isolated zeros
it's just by using power series and continuity

pick a zero z_0 of ur function f
then write out f=sum a_k (z-z_0)^k where z_0 has order k and this holds in some disc of radius r around z_0

then g=f/(z-z_0)^k no longer has that zero but is still analytic in the disc of radius r

but g(z_0)=a_k (nonzero since z_0 has order k for f), so by continuity (our epsilon will be |a_k|/2) there exists delta with |z-z_0|< delta that implies |g(z)-g(z_0)|=|g(z)-a_k|<|a_k|/2. so g(z) is never zero in the disc of radius delta around z_0

Is every diagonalized matrix diagonalizable?
I assume it's true since it's a similar matrix to a diagonal one, since itself is a diagonal one.

Also, is every complex matrix similar to a diagonolized matrix?
I assume it's false since only all square complex matrices are diagonalizable
These questions are so general and i try to find something or prove something but without much success.

>>8134569
Can someone throw his/her opionion in in this?

>>8131537
Notational nightmare.
Hee skipped a lot of steps simplifying the right side.

(x/y)^3 = (x^3 / y^3)

Is the "scientific method" just a meme?

>>8134569
>>8134644

You answered the first question, it's by definition since a matrix is similar to itself via conjugation with the identity matrix.

The second question turned out to have an interesting answer, you should Google it and see for yourself.

Has it ever actually been scientifically proven that the world is round?

>>8134675
As i said i already did look it up and didn't find anything (german) can you give me keywords to search for atleast?

>>8134108
No, you just can't comprehend a simple question.

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>>8133221
>>8133267
Did it with morphological closing, there's room for improvement but it's good enough for now

>>8129493
I bought 500 g of Sodium carbonate and looked up its density (2,53 g/cm3). So I figured 500 g of it must have a volume of around 200 ml. Long story short ... it doesn't fit into my 500 ml container and I don't know what I did wrong. Please help ;_;

>>8135076
The particles aren't very packed so their bulk volume is higher than what you expected?

>>8135075
good enough.
If you want to plug bigger holes, take a bigger structuring element :)

>>8131409
U r 1 dumb cunt, m8

>>8129493
Latex stopped working a few days ago

>>8131630
come on sci

How many possible DNA combinations are there that would still qualify as human?

>>8136205
what are your intentions Frankenstein?

>>8136205
That's a nonsense question. There is no strict classification of species.

>>8131363
holy shit you are an autistic cunt.

If I'm asked to find the value at which the area is minimized, once I differentiated and found my zeroes. If I have two results (plus or minus 1/2 for example), which one do I plug into my area function?
(I'm so sorry for being stupid, I self study because I dropped out of high school)

>>8138115
you have area as a function of the length of something right? since you probably won't have negative distance, use the positive value

>>8138115
It won't matter. An area will be squared anyway.

>>8138157
Thank you! It made sense, when I plugged in the negative value I got a negative area.
>>8138221
In this case it was cubed, so it did matter in the end. Thanks either way

How good a book is Euclid's Elements? Is it 'dated'/difficult/bad? Alternatives? I have never really learned geometry in a rigorous manner so want to try it.

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At what point does a toaster not kill you if it's dropped in a body of water with you in it?

Bathtub = Dead
Swimming Pool = ???
Pacific Ocean = Obviously not

>>8139500
none of those will kill you.
the current will go through the shortest path. It will just short and blow your fuses.

>>8129493
I beat this Sudoku level already

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>>8139276
I've never read it but if you're worried about it being dated you could give it a modern twist

>>8139500
I really really like this picture anon

>>8129493

Hey dumbass. When you make a SQT label it in the topic, not in your name; the way you did it doesn't show up on searches. People made another thread while yours was active because the search returned nothing for SQT.

I'm starting graduate school this fall and one of the courses during my first semester is Cognitive Neuroscience. It's been a good year-and-a-half or so since I've taken any course involving the subject and I have awful severe memory problems.

I was considering emailing my professor to ask something along the lines of "Hi, future student, want to study and refresh myself, blah blah, could you give me any guidelines or specific subjects to review and go over?" I'm already planning to study neuroanatomy but I'm not too sure how in-depth I should get into it. Anyhow, would contacting the professor about this be more of a "Hey, this student is showing interest, let me give him some advice" or would it make me come off as a dumbass?