/sqt/ Stupid Questions Thread

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

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Other urls found in this thread:

en.wikipedia.org/wiki/Lagrange_polynomial
en.wikipedia.org/wiki/Torricelli's_law
schooltutoring.com/help/algebra-how-to-improve-your-factoring/
ncbi.nlm.nih.gov/pmc/articles/PMC3495394/
proofwiki.org/wiki/Banach_Fixed-Point_Theorem
twitter.com/AnonBabble

are hydrocarbons greenhouse gases?

Depends on the hydrocarbon. That's a huge class of molecules. Methane is one though, yes

Why is heroin so much cheaper than other opiates when it's a derivative of morphine? Is it because it's all around a better high and in response to shitty financial situations of addicts?

Are humans the only species where the female will ever ride on top during sex?

What are some good resources for understanding and implementing Li-Fi. I would like to be able to transmit video over an LED for fun just don’t know much.

I understand the converting data into binary and using maybe RS232 or pulse width modulation but am lost at the actual implementation and other protocols

For a reflexive relation of a set to be true, it must be true for all values of a set correct?

Say you have S with [1, 2, 3] if R is m+n=4
S does not have this relation because not all values of S when added to themselves equal 4, right?

>tfw brainlet

Hyenas

If I understand what you're trying to say then the relation set would be {(1,3), (2,2), (3,1)}, so no, not reflexive since (1,1) and (3,3) are not elements of the relation

Thanks very much user, you really helped me. I wasn't formally thinking of the relations applied to the actual relation sets, I was picking them out from all the ordered pairs of the set itself like a dunce. I'm grateful!

Where can I find the proof that there exists no natural number that is neither odd nor even?

use induction

oh, right

are there g forces in a vacuum?

what would the sensation of being pushed feel like in a vacuum?

Do you know a site that lets me put together various different facial parts from any ethnicity of choice and shows the result? I think I'm part indian and greek even though I was born in western europe and all my family in the same area as far as I know, I got kinda curious recently but I don't care enough to spend money for hoax DNA tests, I'd rather go by eye or nothing at all.

N\(E U O) = {}

I forgot, is 0 an even or odd number.

Wait I just looked it up, it’s even

>what would the sensation of being pushed feel like in a vacuum?
Just like anywhere else, except your lungs would be flapping against your face and your blood would be boiling.

Gravity and inertia have nothing to do with air pressure. They work exactly the same in a vacuum.

You mean you were serious?

Which book or course should I look at if I want to get into analysis more formally? I checked MIT's but they don't have the lectures online for that one, just the notes.

Philosophy major here. Turning 26 in April. Should I go back to college and major in STEM? It's either that or grad school for philosophy. I love philosophy and can see myself going all the way but I regret never giving math/science a chance. Is 80k worth the 3 or so years it would take to graduate with a degree in STEM at the age of 29-30?

Thanks.

Google+Photoshop
If you aren't confident with your photo manip skills, there is an image mod thread in /wg/, among other image boards.

If you really want to, I think that you should. STEM is a plethora of interesting information, and it's so broad that there is bound to be something you're specifically interested in.
Do you already have a philosophy degree then, or did you stop going to school?

I feel that it may be more difficult to get an entry-level job when you're 32, though. I would definitely consider getting some experience through internships while you work on your STEM degree.

If objects in space are moving towards us at relativistic speeds, do they seem to age more quickly than objects moving away from us at similar speeds?

Reposting because it doesn't deserve its own thread.

I'm trying to prove that a bijective function F from the euclidean plane to itself maps convex sets to convex sets is an affinity.
I've got that F maps a half-plane with a ray on it to a half-plane with a ray on it, in a way that the origin of the ray is mapped to the origin of the ray.
I would appreciate a hint on how to proceed.

basically, yes. Also, drug dealers dont pay pharma taxes and have less costs since they have no quality control/hygiene control

Is it possible to create a function whose graph passes through any set of points, provided the x values do not repeat?

Only piecewise.

Anyone here familiar with functions? I'm not entirely sure on how to calculate a function and then find the resulting domain and codomain of the resulting function, for example:

Let f : {1, 2, 3} → {a, b, c}, g : {a, b, c} → {10, 20, 30, 50}.

What would g of f be in this instance?

Yes, there are infinitely many such functions. Why the hell is this question being asked here literally everyday?
en.wikipedia.org/wiki/Lagrange_polynomial

how can i calculate the luminosity of a laser diode when i know the wavelength and power consumption of the laser? I'm trying to design a lighting system which uses diffracted lasers rather than traditional light bulbs and want to compare

You want to find a linear T and a vector v0 such that f(v) = Tv + v0 for all v in R^2.
From this, you can see that v0 must be f(0),
Consider g(v)=f(v)-f(0).
Show that g is linear and you're done. Now this is part is obviously the essence of the proof but I can't be bothered to solve it.

>Only piecewise.
Wrong.

>en.wikipedia.org/wiki/Lagrange_polynomial
Only works if there's finitely many points

domain of g of f is the domain of f (you have to plug things into f first)
codomain of g of f is the codomain of g (g gets applied last)

I am having trouble figuring out this problem. if anyone could help me out it would be much appreciated. I know it has something to do with kinetic and potential energy but i'm not sure how to apply it

A spring whose stiffness is 3500n/m is used to launch a 4kg block straight up in the classroom. The spring is initially compressed 0.2m, and the block is initially at rest when it is released. When the block is 1.3m above its starting position, what is its speed?

I think the guy wasn't talking about an infinite set of points.

>I think the guy wasn't talking about an infinite set of points.
Why?

Because he would have specified it otherwise. This means that he didn't know about the finite case. If he doesn't even know about the finite case, you expect him to be asking about the infinite case?

Okay, that makes sense, so g of f is actually a function of its own and not just some operation?

[math] \circ [/math] is an operation; it takes two functions and results a new function, just like + is an operation; it takes two numbers and results a new number.
[math] f \circ g [/math] is the Result of the operation; just like 2+1 is the result of +, it's 3.

See the diagram in the picture.
You read [math] g \circ f [/math] from right to left.

See also this diagram.

>Do you already have a philosophy degree then, or did you stop going to school?
I do. I actually have a double major in philosophy and political (science).

I bought a bunch of physics and math textbooks and I'm going to study them for at least 6 months to see how I really feel about this before I make any drastic decisions. I can't afford to potentially waste time seeking a STEM degree when there's an opportunity cost of completing grad work in philosophy on the line.

Thanks, user.

This is perfect, couldn't have made it more clear, thanks a lot!

Go for it.

Question about finding the eigenvalue and eigenfunction of this differential equation:
2x^2y'' + (λ+2)y = 0

For my first step, should I divide by 2x^2 or should I solve for the general solution right away?

Can someone tell if I did this correctly?
Since this is a Cauchy-Euler equation, I got a general solution by doing 2m(m-1)+λ+2 = 2m^2+λ
Since m= +-sqrt(λ/2), I got a general solution of y(x)= cosh(sqrt(λ/2))x + sinh(sqrt(λ/2))x

From here, should I just assume the 3 cases that alpha > 0, alpha = 0, and alpha < 0?

No. You will observer anyone's wristwatch that is moving at relativistic speed relative to you as going slower than your wristwatch, no matter what direction he's moving. At the same time, he will observe your wristwatch going slower than his.

How do I even start this?
The pressure from the left is holding the water up, but is the standing water also helping to push the water out?

How to find the surface area of some function around a specified axis?

Example:
Find the surface area of [math]y=\sqrt{x}[/math] around the axis [math]x = 1[/math] from 0 to 1

Should I write [math]y = \sqrt{x} +1[/math] and use the definition of surface area?

How do I know when to use a power series solution or two series solution?

How am I supposed to apply Euler's method for a set of equations that has three variables? I feel like I'm supposed to rearrange the equation to make it solvable, but I tried doing so and I didn't get anywhere. Any ideas?

Not exactly sure how to go about it either, but I think this might help?

en.wikipedia.org/wiki/Torricelli's_law

pls help

Is ME a dying field? I don't want to graduate and become a joblet

V= integral of your outer radius - inner radius. and your surface area is the derivative of volume.

seems to be a lot of work
gonna try it, thank you

I'm trying to calculate (roughly) how many megawatts a town might use annually. If I can get the total kilowatthours is it just a simple as multiplying by 1000 and then dividing by 8760 (#hours in a year)?

Brainlet but that doesn't seem right.

Conservation of energy. E_0 = E_1. Total energy is E = mv^2/2 + mgh + kx.

>E = mv^2/2 + mgh + kx.
Meant E = mv^2/2 + mgh + kx^2/2.

>how many megawatts a town might use annually
doesn't make any sense, why do you want to know?

>If I can get the total kilowatthours is it just a simple as multiplying by 1000 and then dividing by 8760 (#hours in a year)?
that would be average power in megawatts over the course of a year

Is this possible?
Factoring site says:
>(100x+50)/(60x+60) can be reduced to (2x+1)/(x+1)
schooltutoring.com/help/algebra-how-to-improve-your-factoring/

>Is this possible?
No.

Is there any scientific evidence of herbal remedies speeding the healing of lacerations, punctures, or other proper wounds? I'm curious if the video game concept of the "mundane" healing potion bears any ground in reality, and the only information I can find is on treatments for shit like body aches, fever, and colds.

Well, I dunno how I failed to find this, but if anyone else is curious: ncbi.nlm.nih.gov/pmc/articles/PMC3495394/

Doesnt really address "herbal remedies," though, and I don't feel like diving down the rabbit hole of Chinese medicine.

Which is going to make me feel more tired tomorrow? Sleeping 3 hours now and then dragging myself out of bed or just staying up? I can catch up on sleep tomorrow night so my question is only for the short-term.

the important question

No, it's pretty stable there just isn't that much technological advancement. Most of the jobs in ME are focused on maintenance or upgrades, nothing groundbreaking, but a lot of older people are retiring now so there's a lot of jobs in ME.

I've read that a sleep cycle is about 90 minutes, so try to get your sleep to be a multiple of 90 minutes. If you wake up mid-cycle you're fucked.

Whats the easiest way to go to space/become an astronaut?

To compare it to the output of power stations in the area annually.

Basically trying to figure out how much power a city would require annually in terms of the energy production of local power plants, but everything on the residential side is measure in kilowatt-hours.

Two, long parallel wires are 10 cm apart and carry currents of 6 A and 4 A in the same direction. Find the net strength of the magnetic field at a distance of 3 cm from the wire carrying 6 A.
I can only figure out how to do current going opposite direction

Is there a way for me to get an iq of over 9000?

You'd need to know the efficiency. The laser isn't going to convert 100% of its power consumption into light (and for frequency-multiplied lasers, not all of the light will be at the nominal wavelength).

Conservation of energy.

Potential energy of a spring is k*x^2/2 where k is the spring constant and x is the displacement from the equilibrium position.

Potential energy of a mass in uniform gravity is m*g*h where m is the mass, g is the gravitational acceleration (9.81 m/s^2 for earth's surface), h is the height (relative to some arbitrary reference point).

Kinetic energy is m*v^2/2 where m is mass and v is speed.

The sum of these three remains constant. In the initial state the third one is zero (mass is stationary); you're being asked to find v in a state where the first is zero (the spring has transferred its energy to the mass).

>To compare it to the output of power stations in the area annually.
you want to use energy, power is change in energy per change in time so adding up the powers over a period of time is going to result in energy

find the strength of the magnetic field from each individual wire at that point and add them together
[eqn] B= \frac{\mu_0 I}{2 \pi r} [/eqn]

The number of dependent variables doesn't matter. And there's no need to rearrange anything.

x(t+Δt)=x(t)+(dx/dt)*Δt
y(t+Δt)=y(t)+(dy/dt)*Δt

It doesn't matter whether dx/dt and dy/dt are a function of x, y, t or whatever, so long as you can calculate them.

Best tablet for reading/writing? I'm looking for something like a kindle (paper-like screen) that also allows smooth writing.

Can anyone help me with the difference in scope between Computer Engineering and Computer Science?

Computer science is focused on the algorithms, data structures, type systems, grammars, etc. Computer engineering applies computer science to software engineering, and includes electrical engineering with all its theory too.

Thank you user.
Seems like picking a major will be harder than I thought, particularly since I'm from a 3rd world country.

>I'm from a 3rd world country.
I'd say engineering in that case, unless you're >150 IQ, but I dunno.

After looking around a bit that does look like the best course of action.
I'll dig around more on MechE (only other career I have even a slight interest in) and decide.
Seems like in CompE you can do your own projects and stuff easier, for obvious reasons. That's pretty appealing.

How come people think that 4 being used instead of pi to determine a circumference generating an imperfect circular shape isn't proof that circumference in reality is the same, as perfectly circular shapes are entirely theoretical?

Of course, estimates of the diameter of such objects would use pi, as such imperfections are commonly immeasurable. The difference does however affect objects in motion.

Circumference in physical reality should then be considered 8r instead of 2pir.

let q be a real number such that 0

Best calculator app for a math undergrad?

With induction you can show that
[math]|a_{n+1}-a_0|

O I see I did shit wrong. Just try to find something close to it then.

So I looked again and it's close to it, but then with a sum so you can prove that it is Cauchy (so use n and m on the left side) and thus it converges because it's in the real numbers.

I can't see where this goes wrong, but a0 being always the limit seems just wrong.

It is similar to tthe existence part of the proof of this:
proofwiki.org/wiki/Banach_Fixed-Point_Theorem

Oh I see where it is wrong.
It's [math] |a_{n+1} - a_n| < q^n |a_1 - a_0| [/math] , not [math] |a_{n+1} - a_0| < q^n |a_1 - a_0| [/math] .
If it was just a typo and you meant that [math] |a_{n+1} - a_n|q^n |a_1 - a_0| [/math] implies Cauchy, then that's not correct.

Are the wavefunctions for a hydrogen-like atom eigenfunctions of the Hamiltonian?

I was just trying some shit that's incorrect.

But like I said use triangle inequality and my halfly correct idea to end up with the sum as in the "from which it follows that" part from your link to the fixed point theorem.

No no you retard, they are the Hamilfunctions of the Eigentonian.

What?

same poster here, another question:
I had the idea of proving convergence using Cantor's lemma. I know it's not the easiest solution (and I already have different proofs), but I'm curious to see if it could be done.
Does anybody have an idea on how it could be done?

Is it true there's no black people in upper level math classes? Am I just wasting my time studying? Am I physically incapable of learning high level math? I have an IQ of 120, not that I think IQ really matters all that much

It's only true if you quit now.

No you retard. If you are black it doesn't mean you are stupid; it is just more probable.