Stupid Question Thread /sqt/

This thread is for questions that don't deserve their own thread.

Tips:
>provide context
>show partial work
>use wolframalpha.com and stackexchange.com

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was thinking why is the bond strength between H2 higher than that between F2?

How long would it take to complete the following:

Algebra and Trigonometry - Judith Beecher

Elementary Calculus - Keisler

Matrices and Linear Algebra" by Schneider and Barker

This group is spreading false information regarding cancer causing people to refuse proven tx in lieu of buying into their narrative. Please help expose them. Idk how to do this but I have read enough about Veeky Forums to know there are intelligent people here who can make a difference.

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prove the palindrome language over {0,1} is not in DCFL without using the pumping lemme for DCFL

My best attempt so far looks at the grammar and basically says it's impossible to find a deterministic context free grammar that creates the palindrome language.

I was revisiting high school physics and a book said a current produces a magnetic field. If that's so, then will leaving a small coin next to the wire make it attracted? If not why?

And why does cutting a magnet in half create two other magnets?

I was looking through the yeast that settle at the bottom of the jug while making beer and i keep seeing these square looking things,
any idea what these are?

The reason here is that there are less electrons in hydrogen and they repel each other lesser than flourine would do.

The magnetic field strength in a current carrying conductor is related by F = BIL, where F is the normal force experienced, B is the magnetic field strength and L is the length of the conductor. The magnetic field strength is actually very small. (Earth has about 50 microtesla. The MRI scanner reaching about 3 tesla.) This results a small force that cannot do work against the resistive forces present.

Magnets actually have "domains" or simply region of space where the area has same direction of magnetic strength. (Pic by earlier post) Cutting it into half will simply cause a new resultant magnetic field being created by the domains.

WHAT THE FUCK IS "FIRST 9 WHOLE NUMBERS FROM THE RANGE OF VALUES"?!

IT DEPENDS ON FUCKING X.

WHAT THE FUCK?! PLEASE TELL ME FFS.


The median of this bullshit should be zero. Which IT FUCKING ISN'T HOWEVER YOU TRY IT FFS.

I need a method to study abstract proof based math

I'm going through my first class with it and the proofs on exams are killing me and it takes me forever to go through the homework

My professor says I present a lot of logical but not-quite-correct ideas in my work and office hours and that I simply must practice my proofs more

But how! There are no answers in the book and I rarely know if I'm 100% correct when I write something. How do you practice writing proofs effectively

So basically a domain is like the lego bricks that make up a magnet, right? Meaning if I split one Lego made of 20 blocks I just get two blocks made of 10 Legos instead. But what if I divide those as well to the point I end up with 20 blocks of one Lego each. And then hammer each individual Lego. I was thinking about that "quanta" thing, that energy is stored in packs that cannot be divided. So following the analogy does the magnetic field just stop existing altogether?

Why is there a difference of voltage when resistors are in series, but not in parallel?

The closed form solution is [math]y = x^2 - x[/math], but your question makes no real sense. The range of the polynomial is -1 to infinity, so it could mean {-1, 0, 1, 2, 3, 4, 5, 6, 7}, the median of thse values being 3. The only other thing it could mean is if your function was a probability density function, which it isnt. So you're probably better off asking your teacher/lecturer/whoever what their vague ass question means instead of yelling at us.

How come there are so many foods that are perfectly okay for humans to eat but can be harmful or even fatal to dogs and cats even in small quantities?

Are there any foods that dogs and cats can eat that are fatal humans? Or do we don't know because we usually don't feed our pets things that kill us?

Why wouldn't this scenario break the law of conservation of energy?
>You have a gun that shoot a bullet at 100m/s
>You can run forward at 5m/s
>You run at 5m/s and shoot the gun at the same direction you are running at
>The bullet goes 105m/s

Since [eqn]KE=1/2mv^2[/eqn], why does the kinetic energy that takes to run at 5m/s from 0m/s, also make something go from 100m/s to 105m/s when there is a squared relationship on velocity?

someone please answer this

>The reason here is that there are less electrons in hydrogen and they repel each other lesser than flourine would do.
thanks bb

voltage across what?

If the average time is 16 seconds for a car to travel 5km how do I find the average speed

the you-bullet system has a total kinetic energy of K. It also has some chemical energy stored in the gunpowder. When you fire the bullet, expanding gases do more work on the bullet than they do on you (work done on you is negative, because the force opposes system's motion), thus increasing the system's total kinetic energy.
Momentum, however, is conserved, since no outside forces are at work (gases push the bullet forward with equal force that they are pushing you back with)

Here's an example. A circuit with two resistors in series. If you plug a voltmeter to (1) and (2), and then to (1) and (3), you'll see there is a difference in the voltage measured. Hence if you sum all voltages it will be equals to the overall voltage. So the question is how exactly does this work and why is it happening.

there will be zero volts between 1 and 2.

Point 1 and point 2 are the same point. There is 0 ohms between them since in a schematic, a wire has no resistance. That means that they will have no difference in electrical potential.

if both the resistors are the same, there will be .5v+ across 1 and 3, and then .5v+ across 3 and the positive terminal.

distance divided by time

Can somebody explain in an intuitive way why multiplication by the Jacobian matrix results in a transformation of coordinates?

I see how it works in practice -- like for example transforming rectangular coordinates to polar coordinates and vice versa -- but to me it's just "magic" that multiplication by the Jacobian matrix accomplishes this transformation.

Is there some bit of insight that will show me why the Jacobian does this?

Thanks.
>if both the resistors are the same, there will be .5v+ across 1 and 3, and then .5v+ across 3 and the positive terminal.
That's assuming this is a 1.5V battery right?
Look at this example now. Can you help me? To me it makes more sense now, btween 1 and 2 in there's zero voltage. But now look at this picture I made, with improved graphics. How would I calculate the amperage and the voltage in different points of these two circuits? And why is there a difference in voltage when you measure stuff between two resistors?
PS I hope it doesn't come out as I'm some highschool kid, I'm an adult.

Also another thing I don't understand is why must there be always a ground attached to circuits? I'm using a "circuit simulator" app to experiment and relearn these things, but my circuits never work if a ground part is connected to the circuit. Why??

The voltage of the battery would not matter if you built that original circuit. It would be half of whatever the voltage is across each resistor.

No matter what resistance you have, the negative terminal will always be 0v and the positive terminal will always be whatever voltage the battery is.

So divide 1 by the sum of all the resistors' values. What you have is the voltage drop of one ohm. Start at the positive terminal. multiply it by each resistor to get the voltage drop. across that resistor.

To find the current, find the total resistance. For resistors in series, it is the sum of the values. Then you solve the equation v = current*resistance given the voltage of the battery and the total resistance. This does not change at any point in the circuit.

The ground is necessary because there has to be a difference. Otherwise, there is no reason for the energy to leave the battery.

remember: the minus terminal of a battery = 0v = ground

I kind of understand it better now. I think so. Let me see if I got it right. In the example at , the "voltage drop" would be 0.5 and 0.5 if resistors were the same size. So in the left example at , the first voltage drop (5 ohms) would be 4 times the size of the second voltage drop (20 ohms) (5:20 = 1:4), in such a way the sum would be equal to 100? So we would have 20 and 80?

And if the two last lines you wrote are true, then why do batteries work the way they do? I mean, let's say... I'm an astronaut, and I'm floating in space. If I hold a phone in space, the phone would still work if the battery is charged, right? It's not connected to any ground, it's in fucking space. So what exactly is this ground? I understand an earth wire or whatever the technical name gives a kind of infinite sink for electrons because it's so massive compared to the circuit. So how come things with batteries supposedly work without being attached to earth or comparable body?

"Mains earth" AKA "earth" is the wire that is connected to the dirt.

Some people in the US call what is really earth "ground", but that's just retarded.

You would use earth when you want to prevent something from becoming charged and shocking you. That's another topic.

Battery minus = 0v = ground =/= mains earth.

A real life battery that would work in space or on Earth is made by taking one chemical that has too much electrons, another chemical that wants more electrons, and then insulating them from each other. One chemical is - the other is +.

Thanks. I think that answers most my questions.

Actually here's another question on electricity. I was reading and it seems electrons in a circuit travel anywhere between 50% to 99% of the speed of light. Aren't those relativistic enough to, for the lack of a better term, fuck up spacetime? If yes, what exactly are the practical effects of a circuit with a current flowing in relativistic speeds? Do electrons in relativistic speeds have anything to do with magnetism?

Are there any scientific things that are shaped like the pseudo-scientific Kabbalistic Tree of Life? Mathematical graphs, molecules, etc.

have you ever had a physics 2 or higher class yet? or are you just spouting buzzwords you found online?

Drew a picture showing a circuit in the form of the water analogy that is commonly used where it is thought of as water flowing through pipes and resistors are pipes with smaller diameter, etc... I labelled voltages of each resistor to show how a circuit may work with resistors in parallel vs series. In parallel, the two resistors pipe water from the same starting pipe to the same end pipe so the voltage (potential difference) will be the same as they are the same initial and final pipe. In series, the voltage of the 1st resistor will be the potential difference between the initial pipe and the water just after the resistor. The voltage of the 2nd resistor will be the potential difference between just after the first resistor and the final pipe. Of course this value adds up to 5V still because they are the same initial and final pipes.

Why doesn't the electron just take the shortest path? For example, in this image, why doesn't the current flow only through 8721? If the current exists because of the negative side repelling electrons and the positive one attracting them, why wont electrons just follow the shortest path? Let alone be spread evenly across the paralel circuit when resistors are equal? Also why is the speed the same in all parts? Why don't electrons go faster when they are close to the battery than they are when they are away, if Coulomb's law has distance be one of its factors?
No, I'm a 20 something yo highschool dropout studying highschool things. I don't know the correct terms. All I was pointing out is the electrons move in speeds very close to the speed of light according to all sources. And I know crazy things happen when you approach the speed of light. Like time dilation and lengthy contraction. The effect increases exponentially around 80% of c. So I asked what that means for a circuit. What happens when you have a circuit with amperage at 99% the speed of light. From an electrical point of view that is. I also know circuits have something to do with magnets so I'm wondering too what's the connection between relativity, speed of light, electricity and magnets. Yes you may say for now I'm just spouting buzzwords I found online but this is like my third day of physics. How much time of study did it take you to learn the things I did in three days? Including so far transistors, capacitors, even logic gates, relativity, superposition, tunnelling etc. For now its all just theory but I'm excited to jump into the math.

Wrong image. Sorry. use this one for reference.

Is there a way to algebraically find the solution set of x of f(x) = 1 if the solution set would be something like (0,2),(4,5),(9,10)

>I was reading and it seems electrons in a circuit travel anywhere between 50% to 99% of the speed of light.

No, electric fields move between 50% to 99% the speed of light but electrons don't. They drift along with the current at only 1.38mm/minute (for comparison sperm moves at 4mm/min) and they move around randomly at around 1570km/s (less than 1% of the speed of light).

>Do electrons in relativistic speeds have anything to do with magnetism?

Magnetism is a relativistic effect.

You have current on all 3 paths, just on different levels. According to Ohm's law, there will be more current on the wire according to its resistance, so we can say Ir3>Ir2>Ir1. But then, back to your question, why doesn't current just flow through R1? R1 and R2 are more conductive than R3, this way it's easier for electrons to partially flow through all 3 wires, in inversely proportional amounts to each wire's resistance. So, again, Ir1>Ir2>Ir3

>The closed form solution is [math]y = x^2 - x[/math],
pls expand

electrons will always try to minimize a potential difference if one is present (the battery). in circuits and parallel resistors the potential difference manifests itself across all the resistors. since there's a potential difference across the resistors the electrons will want to move through it. if the resistances are all relatively the same the electrons will go through the resistors at relatively the same rate [math] I=\frac{V}{R} [/math] (ohm's law). if one resistance is significantly lower than the others than you observer a "short circuit" where most of the electrons will go down the lower resistance path. but physically there will always be electrons going down each path because there's always a current if there's a finite [math] R [/math] in [eqn] I=\frac{V}{R} [/eqn].

so to sum it up, battery manifests potential difference across each resistor. electron wants to minimize it. electron moves through all of them because potential is across each one

How the fuck do I learn complex analysis in one day?

>How the fuck do I learn complex analysis in one day?
Go to the North Pole and study there

Could you walk on the outside of a Dyson sphere? How hot would it be? Could it have an atmosphere? If there was a missing panel how close could you get to the hole? What would happen to the atmosphere? What's stopping the sphere from getting misaligned and crashing into the sun? What would happen? Other than a fucked up sphere, obviously.

Can anyone here explain the difference between these formulas (the standard errors)

i.imgur.com/CJNljub.png

so 5/16? This gives 0.3125 and doesn't really seem right for an average speed of something

Someone pls help

consider the geometric implications of a matrixdeterminant in general

also this addresses your question well but it's in czech math.feld.cvut.cz/tiser/iweb3.pdf

[math]\int_{0}^{+\infty} \frac{1}{(1+t)^{2}(1+t^2)}[/math]

is it possible ?

HOW DO I KNOW THE RANGE OF VALUES OF THIS FUCKING THING FFS?!

>is it possible ?
Pi/4

how?

please I'm struggling for a long time

[math]\int_{0}^{x} (k + 1) dk = [\frac{1}{2} k^2 + k]_{0}^{x} = \frac{1}{2} x^2 + x[/math]
Understand? Now stop fucking crying, it makes people not want to answer your question

>how?
>please I'm struggling for a long time
[math]\frac{1}{(1+t^2)^2}=\frac{1+t^2-t^2}{(1+t^2)^2}=\frac{1}{1+t^2}+\frac{t^2}{(1+t^2)^2[/math]
The first one gives you an ArcTan and the second one gives you t/(1+t^2), with appropriate coefficients.

As with most integrals, substitute t = tan(x), after that its ez ez

>[math]\frac{1}{(1+t^2)^2} = \frac{1+t^2-t^2}{(1+t^2)^2} = \frac{1}{1+t^2}+ \frac{t^2}{(1+t^2)^2}[/math]

[math]\frac{1}{(1+t^2)^2}[/math]

how to get this?

what to do after?

sorry for being a brainlet just need more details

Well that's what I fucking get and it makes no fucking sense so

Well for one, this guy got it wrong, the answer is 1/2. For two, tan substitution might not be the best way to go, although it looked a good pick as it makes 2 terms immediately cancel, it still works though but its a pain.
What I would now reccomend is substituting t = 1/x and doing some tricky shit that I just did, i'll give you a write up in a second

Oh It's ok I found it :

[math]t = tan(x)[/math]

[math]\int_{0}^{+\infty} \frac{1}{(1+tanx)^{2}(1+tanx^2)} (1+tanx^2) dx[/math] = [math]\int_{0}^{+\infty} \frac{1}{(1+tanx)}^{2}[/math] = [math]Arctg(+\infty)[/math] = [math]\frac {pi}{2}[/math]

I hope this is right, thanks guys

oh... so isn't right?

I'm afraid not, you got the last integral wrong, arctan(x) does not equal that, and you didn't substitute the limits correctly.

oh yeah I didn't see it clearly, I'm very lost

could you type the steps please?

Too much to type out so I wrote it, I have the handwriting of a 3 year old and sometimes skip steps, sorry
Its a difficult integral and this is a fairly abstract way to do them, typically when you do an integral like this where you need to preserve the limits to be able to manipulate it you'll do t = 1/x for 0 to infinity, and t = 1 - x for 0 to 1, if that makes any sense

I have a sine graph that shows the depth of water over time. I need a formula that I can use to find for how many hours the depth is above a certain height.

Any good books on Computer Vision?

How do I create a rubik's cube animation like this from scratch?

youtube.com/watch?v=xlwORzo2OJ8

t. brainlet who likes Image Processing

Do definite integrals find the area for the inclusive or exclusive domains?
\int_{a}^{b}f(x)dx finding the area for x \in (a, b) or x \in [a, b].

The area should equal the same value, just wondering if this is a question that should be asked.

Wow this is brain melting

but can we write : (1+1/x)^2 = 1/x^4(1+x)^2 ??

I had to precise that the question of this equation says :

Solve ( if possible ) [equation]

ive asked this question countless times with no replies but: does anyone know if 2 summer REUs would be enough research experience to get into a top 20 EE phd program? Im looking to get into umich or uiuc if thay matters.

No, but you can write (1+1/x)^2 = 1/x^2(1+x)^2
[math](1+\frac{1}{x})^2 = ((\frac{1}{x})(1+x))^2 = \frac{1}{x^2} (1+x)^2[/math]
I also took a factor of 1/x^2 out of the (1+1/x^2) term

dude thanks a lot, but If I got this in the exam I'm not sure I would be able to do it

Its a pretty horrific integral, but if you wanted questions that need you to do stuff like that, check out the integral questions on some STEP papers, thats where I learnt it

I just realized my shit level in maths, even though I'm physicist, I will try to catch up this summer and I hope I pass this semester.

what you do to help improve your level ?

The only way to get better at integrals is a lot of practice doing integrals, first it will build up your intuition of when to do different techniques, then it will build up your mental vault of patterns so you can just recognize some integrals from the sight of them. There isn't really a shortcut.
This is assuming you already know the techniques; substitution, integration by parts, partial fractions, etc.

yeah, I know all the tricks, but don't have that quick wit to tell what should we do at first glance

Can someone help a brainlet like me understand spatial autocorellation?

What I'm having trouble understanding here is the term w. I understand its the weight of some shit obtained with a weight matrix, but what is it conceptually speaking? Is it a decimal that is meant to lower the degree of correlation if the variables are not well clustered?

The weak force is a Jewish Meme designed to keep you unaware of Quarkstein's Number.

Dog shit cleans the skin off leather. It's that simple.

Because we are bigger, and have evolved to be omnivores. However, cats and dogs being carnivores gives them a greater tolerance for things like raw meat than us.

> implications of a matrix determinant in general

Thanks. I already have a good intuitive understanding of how the determinant specifies how much the area scales when performing the matrix multiplication.

What I'm hung up on is trying to figure out why its the act of taking the *partial derivatives* that achieves the correct transformation.

I do understand how the Jacobian directly maps a tangent vector from the domain into the corresponding tangent vector in the range. That's because the tangent vector is determined by the derivatives -- and obviously the Jacobian is supplying those derivatives.

What I'm missing is that final bit of intuition about why the Jacobian also achieves the coordinate transformation for the actual function value itself (and not just the tangent vector).

Everything I read focuses heavily on the determinant, which I already understand. I guess I need something more basic, which is why the derivatives are taken in the first place, and how its geometric interpretation (i.e. the tangent vectors) leads to the transformation of coordinates.

I plugged a battery into my Akai TV remote and it destroyed spacetime. That was in March.

could someone provide me a proof for pic
thanks

We should all be IN CZECK!!

...

thanks mate

It doesn't supply the value for the function itself, only the area thing. You use function composition for the function value.

can an element of a subset be a function? And can that function be used for mapping particular subsets?

like if f is an element of F, can I say for some arbitrary process f:O->R where

Am not sure if my question qualifies.

Could someone give me a quick rundown of how pic related is deduced?

It is used as part of a proof for the prime number theorem but no comment is given about it. The author just pulls that inequality out of his ass and me never having worked with the logarithmic integral I do not know how that is deduced.

when t is between 2 and sqrt(x) you have
log2

Ah, that's right. Pretty simple too. I thought it would be more complicated because it gives a really strong bound.

You see, what is being proved is that when you divide that integral on the left by x, and then take the limit to infinity then it gets to 0.

And when you take the inequality on the right and divide it by x, and take the limit to infinity it still gets to 0. So with that really inneficient approximation you still get the bound you need.

Thank you my man, I'll see if I can figure out the other part on my own.

Hope my drawings good enough, he's effectively comparing the areas of the 2 boxes and the integral, he could make it stricter by removing the far left bit but he hasn't, no clue why

i fucked up and made a new thread, anways

help a brainlet out

im supposed to use software such as matlab, sagemath etc to solve this exercise.
hope my translation is understandable

first im writing the function as this to use in software
c(x)=((pi)((300/cos(x))2)0.8)/((pi/2)(14)2(1+sin(x)-0.5*cos(x)))

is that right?

now

problem: considering h=300, F=0.8 and D=14, find the positive angle A inferior to pi/25 for which C=1200.

a)find a function f(x), for which the solution of f(x)=0, is equivalent to the solution of the problem.

i dont understand this question at all, also here's the original in portuguese: encontre uma função f(x), cuja solução de f(x)=0, seja equivalente à solução do problema questão.

b) make sure that in the interval [0,pi/25] you can use the secant method

im not sure here i think f has to be differentiable twice in the interval and that f'(x) cant have roots in the interval correct?
i dont have to worry about if f(0)*f(pi/25) is less than 0 right? because it isnt

This was the question:

"Compute the equation of state of a Fermi gas where its chemical potential is negative. Use the relation between pressure and the grand canonical potential."

propositional logic, stanford or mit website
also the book "How to Prove It"

If I have a group of order p^n, how do I show all groups of order p^(n-1) are normal subgroups?

>Make friends with math majors/grad students/professors
>Have them check your proofs

Or LaTeX them up and post them here so we can relentlessly mock you.

>relentlessly mock you
this is a no bulli zone

is there actually going to be an era of black holes where stars never form again, or is this just speculation based on what we know?