/sqt/ Stupid Question Thread

>when you are in space ...

Maybe we could measure Doppler shifts in the CMB in various directions to determine how fast we are moving in said directions? We still need a reference point, but the CMB works well.

>also if our galaxy is ...

To answer the second part first, the expansion of the universe causes superluminal recession of objects far from us. The laws of physics are not being violated. In their own frame, these objects are perfectly happy. The essential issue is that we are interested in 'general relativity' which allows the situation we see; locally these objects are described by special relativity and within that framework nothing 'locally' is wrong.

en.wikipedia.org/wiki/Metric_expansion_of_space

For the first question, it's a little more thorny. This is the notion of different types of horizons in cosmology. If we have objects moving apart at a relative speed > c, then it is possible not to see them. If depends on the exact evolution of the expansion of the universe. If it's speeding up, then we will never see these objects again. If it's slowing down, we will eventually make contact.

There are several horizons to talk about and it is an interesting subject. I will write a more detailed response a bit later.

why is moving air colder than air that doesn't move? shouldn't the friction make it hotter?

Moving air 'feels' colder which is an entirely different proposition from being colder. It's because a larger number of air molecules are passing your skin which takes away more heat, making you feel colder. That's how fans work - they don't make the room any colder.

>they don't make the room any colder
true, i didn't think about that. thanks for your answer!

Moving air is not cooler.
You feel it cooler because moisture is vaporising on you are skin, returd.

>returd
i came to the right thread then

To add to my answer:

In fact, if we define temperature as proportional to the average kinetic energy of the molecules (which is proportional to their speed squared), then a high temperature room should have molecules moving very fast and vice versa.

The increased KE of, say, a desk fan moving the air molecules is more than offset by the cooling effect on your body. The work that the fan is doing i.e. the energy required to run it is, in fact, making the room very slightly warmer (plus resistive heating the electronics, friction with the air makes the room hotter too). However, the net effect on you is that you feel colder purely because of the cooling effect on your skin.

There's no trickery or violation of conservation of energy here; it's just due to how your body manages/interprets its temperature. I suppose if you were in a perfectly thermally insulated room with a fan going, the constant power consumption would eventually heat up the room!

Not true when a =0

that's very in-depth for such a simple question, thanks again!

are there any 'optimal' ways to cool something? i know that freezers for example generate a lot of heat on the outside.

i've always wondered why computers usually use fans for cooling

how is it true for every other a

note that [eqn]f(x)= b^x-x^b=e^{x\log b}-e^{b\log x}\Rightarrow f'(x)=\log b \cdot e^{x\log b}-\frac{b}{x}\cdot e^{b\log x}=\log b\cdot b^x-\frac{b}{x} x^b[/eqn]

there are infinitely many possible a values that give only imaginary roots....

I honestly don't know how someone that studies medicine doesn't become paranoid as fuck.

...

That geometry equation you posted comes from part A. Also what is your question? This is stupid questions thread not stupid people thread.

Well 3b asks what it implies if S=0. S cannot be a negative number because it's made up of a sum of squares, So if it's 0 all the terms must also be 0 and that implies that all the points lie on the line D. What class is this for?

Fans are used for cooling because it turns the air into a heat dump. It's the same reason people use fans for cooling, the computer "feels" cooler while the room increases in temperature.

We're basically pumping in some cool air and although the act of moving it increases the temperature of the air, the computer heats up the air much more drastically. This hot air then exits into the world through a vent and more cool air is pumped in. Basically the act of moving air (convection) doesn't heat it up that much compared to how much the computer heats the air (conduction).

(1/2)

Fans are used in computers because they're cheap, simple and mostly effective. There are downsides (noise, dust), but most people are pretty happy because it's sufficient for most PC needs. Modern liquid cooling systems are not too pricey these days, but still require a bit more thought and care to install, plus the risk of a leak is always there (inb4 /g/-tier debate on PC cooling systems).

Supercomputers use a lot of liquid cooling or even liquid immersion (thermally conductive but not electrically conductive fluids). This is because the higher specific heat capacity of water than air makes it more effective (price is no real object in these cases).

Anyway, regarding optimal cooling: In simple thermodynamic terms, to cool something we want to take heat from somewhere to make it colder. Typically, as with a fridge or freezer, we want to take heat from the cold fridge to the surroundings*. Now, heat naturally flows from hot to cold, so in order to reverse this natural order, we have to do 'work' i.e. expend electrical power.

There are limits on fridge (or any cooling system - we just use the term fridge to contrast 'engine') efficiency, but they are set by the temperatures that you're working with. Plus, these are theoretical limits - it tells you nothing about how to action them: physics.weber.edu/thermal/refrigerators.pdf

*Lots of fridge operate by cooling their contents down, then shutting off. When the temperature inside goes up (heat naturally flows from the environment, assuming it's room temperature) it switches on again. It's still cooler than the surroundings, but not as cool as it could be.

>Why is Physics harder than it should be for a computer engineer major?
Because computer engineers are stupid.

lmao retard, V=4/3 pi R^3 is standard, you just have to rearrange for R

(2/2)

IRL, they're designed to dump heat to the outside (explainthatstuff.com/refrigerator.html). You can improve the efficiency of a fridge by placing it in an airy room. When the heat is dumped outside the fridge, you want to get rid of it (c.f. the PDF that I sent you - you want to lower T_H). Hence, put it in an airy room where air flow carries the heat away (much like we discussed with human skin).

So there are ways to improve efficiency, but there are always hard limits. Plus, it might be a case of diminishing returns. You could spend masses of money on making a cooling system incredibly efficient ... or you could just spend the money on a couple of solar panels and use a bit more power.

Now if you are talking about 'optimal' in terms of rapid cooling, then we should be clear about what sort of cooling is going on. I imagine we're talking about conductive cooling i.e. heat flows from hot stuff to cold stuff when they're in thermal contact. In this case, the speed of cooling i.e. the rate of change of temperature can be approximated with Fourier's Law en.wikipedia.org/wiki/Thermal_conduction#Fourier.27s_law . Intuitively, on a hot day, you cool down faster sat in a freezer than a fridge.

Hence, to cool rapidly, we need a large temperature difference between the hot object and its surroundings. It's entirely possible to manufacture this if you're willing to invest money in complicated cooling methods in order to cool some object of interest rapidly. But it involves a lot of money and work. Plus, you're can't make anything more 'efficient' than we discussed. It might be quick, but you had to put in all the work to cool everything down in the first place. It would be like running liquid nitrogen through a PC's liquid cooling system. Sure it's fast, but you had to make the liquid nitrogen in the first place. And even then, you don't need your PC at ~80k; you need it at ~320K.

>You can improve the efficiency of a fridge by placing it in an airy room. When the heat is dumped outside the fridge, you want to get rid of it (c.f. the PDF that I sent you - you want to lower T_H).
I don't think so. Efficiency=1-Tc/Th
Making Th closer to Tc would actually lower the efficiency. Like you said in your 3rd paragraph, you want there to be a greater temperature differential. Besides, you can't really change the efficiency of your fridge, it's a fixed number that depends on the machinery. Since Efficiency is fixed, Tc/Th must also be fixed. So lowering the temperature of the room (Th) would only decrease the temperature of the fridge (Tc). I guess you're still making the fridge better but I don't think you're increasing the efficiency.

Can anyone help me what I am doing wrong? The answer is suppose to be 7305s.

There are actually 365.25 days in 1 year.

What does it mean by "what is the total of the daily increases in time?"

>what is the total of the daily increases in time?
you take all the daily increases and total them up.

why can't we put protons, neutrons and electrons together to make different elements?

Who said we can't make different elements? We do it all the time. Just bang shit together. It happens to be ridiculously expensive but once we get our Dyson swarm rolling we'll have more energy than we know what to do with. It will likely still be cheaper to dig up gold than to produce it, though.

Really? Wish I knew that.

increases from what, the original day length or the last day?

Help us out here, feeling like a Brainlet.
I have these equations:
[math]T_{1} sin(\theta_1)+ T_{2} sin(\theta_2)= mg[/math]

[math]15 sin(\theta_1) = 20 sin(\theta_2)[/math]

[math]15 cos(\theta_1) + 20 cos(\theta_2) = 25[/math]

[math]T_{1} cos(\theta_1) = T_{2} cos(\theta_2)[/math]

I just can't find the horizontal and vertical lengths of each string.

For what equation is this Polar coordinate graph possible?

Is it possible to put gills on humans so we can breath water like fish do?

Any suggestions what I should study?
I got accepted to MTU and if I go to spend four years in a desolate wasteland I have to study something I like.

What's the most Chem like major that works on/with the development/testing of new chemicals?

I have a deep interest for electrical engineering.
But I have no clue where to start.

Does Veeky Forums have any pointers?

Any math up to Diff EQ you're spotty in
Logic gates and vhdl shit
Circuits and shit
Industrial systems if u got the time

That's like saying you have an interest in food.

What part in particular interests you? Analog circuits? Wiring your home? Microcontrollers? FPGAs?

desu the flow of electrons is what i find interesting.
So I guess analog circuits?

What is consciousness?
Is there such thing a soul?
Do we live in a simulation?
What is the meaning of everything? How everything came to be? Big bang? what caused it? what coused it that caused it, you can ask that question forever, science will never reach the answer, even in billions of years, you can always keep asking why?
Is that the proof of God?
Or maybe humans are just too stupid to understand, maybe there is a "higher" level of consciousness, maybe there are beings that are to us what animals are to us?

maybe there are beings that are to us what we are to animals?*

Looks like r=sin(5a/2).

those are some gay questions lol

Help me please

m/n*b=1
mb/n=1
->if you do cross-multiplication, you'll get
mb=n
b=n/m
Thus b = n/m

a=m/n
Let b=n/m
Then ab = mn/nm=nm/mn=1

Nah I tried it on a graph.This is not it.

You guessed, an exercise require to find out answer via math, just as did

Congratulations. If u knew some classical physics and had asked yourselF those qiestions you would have been on your way to discover relativity and were on your way to become the most well known genius ever. However einstein did all this 100 years ago, so all ican do now is call you an idiot and tell u to study relativity

Why can't I just do things?

In a group:
if aa'=ab=1, then a'aa'=a'ab implies a'=b so we have unique inverses

Q\0 is a group under multiplication

Therefore since b=n/m is an inverse, it is the only inverse.

Oh it just asks for a number. What are you busting my balls for then?

I just though that guessing never was math's books method.

Can anyone recommend a good book as an introduction to quantumbrella mechanics? I've worked with QM previously at uni but it was more like describing how electrons behave as opposed to actually explaining it

By 'efficiency', I meant coefficient of performance i.e. heat moved per unit work done (which may be greater than 1). It's all in the PDF I mentioned.

You do mean quantum mechanics right?

There was a thread yesterday:

Ah I totally forgot when talking about refrigerators the efficiency becomes the coefficient of performance. Sorry about that!

I heard somewhere that crows are really good at memorizing faces of humans, and no when to flee when a specific person comes around.

Someone explain to me why is pic related the case, this is for counting the number of permutations of n objects, n_1 of which are alike of one kind, n_2 of which are alike of another kind, ....,n_r of which are alike of
another kind.

In general,how the fuck do you understand probability? I am autistic enough that I hate being spoonfed math formulas, what did you guys read to reach chill level with probablity?

FUCK here it is.

you must be that edgy kid sitting at the edge of the room telling people he hates everything

It's really the same argument for why the formula for the binomial coefficient is what it is.

Imagine putting all the objects in some order (there are n! ways to do this) and then putting the first n1 in one bucket, the next n2 into another, and so on. Now the question is: how many different orderings will give me the same configuration (i.e. the same objects in each bucket)? Well, if you reorder the first n1 objects (n1! ways to do this), you get the same configuration, and similarly for the other groups. So for each configuration, there are n1!...nr! (from reordering all the objects in each bucket independently) different orderings that correspond to that configuration.

You have limited mental resources. The mind gets tired out so you need to rest.

how to be better at math and motivate myself for it? and not just calculus, just math in general.

I've had a shitty teacher so I'm kinda traumatized

I sort of get it, but what I imagined is pretty different than yours. I imagine n slots, then fill them with n items, sure there are n! ways to do this.

But let say given 10 items, I put them in ordered slots and 3 of them are the same. So I imagine that the rest of the 7 slots are faded out and I count the number of ways to order three items.

kek you're in for a rough one

Describe in words the centrifugal and centripetal components of acceleration and their respective effects

so for the top part, you have a pot of [math]n[/math] different options you can put in the first place. For the second place, you have an option of [math]n-1[/math] things, for the third, [math]n-3[/math], etc. Hence you have [math]n*(n-1)*(n-2)*...*1=n![/math].

Now suppose you choose one of the possible [math]n![/math] options. From those [math]n[/math] places that are chosen, there are a number, namely [math]n_1[/math], that are repeats. So without changing your chosen combination, you can move around these repeats to give you the exact same combination. So if you remove the repeats from their place, you can place them again in the order you want back to where they were. Repeating the same argument, you have exactly [math]n_1![/math] permutations of where to put these repeats. So you take away these extra permutations by dividing the total number of possible options by the possible repeats.

Now repeat the same argument for another [math]n_2, n_3, ...[/math] repeats.

explain the difference between curvature and torsion. Is there any link between torsion and torque?

Torsion is twisting out of the plane of curvature. Curvature is exactly how you understand it now. A circle has no torsion, but a helix does.

Torsion is geometric and describes the twisting, while a torque is what twists and untwists it

not everyone has to like math.

sometimes applications to a field (electrical engineering, physics, machine learning, etc.) will help motivate a topic. other times the person just likes the subject and is curious about discovering why things work (why are derivatives inverses of integrals? why does trapezoid rule work? how can we extend calculus to 3D?)

(a) What is a smooth curve? (b) Give an example of a curve in 3-dimensional space curve that is not smooth.

wolframalpha.com/input/?i=polar plot r=sin(5/2*(theta+pi/2)) from -pi/2 to 3/2*pi

The other user was right.

open a textbook for the technical definition of smooth curve C but its basically if you take a parametrization f: real numbers -> C it should be infinitely differentiable, for example sin(t), cos(t), exp(t), t are all smooth

a non-smooth curve includes things like {(0,y,0) : y >= 0 } union {(x,0,0} : x >=0 }, where the curve is not smooth at the origin and your intuition should indicate this since you change direction in a very 'jagged' way

Thx user.

Thank You.

Describe in words the centrifugal and centripetal components of acceleration and their respective effects.

Retard here, I can't fucking do proofs worth a shit Veeky Forums pls help

Let an = (1/3)^n, prove it converges to 0
I have the following:
Let ε>0, need |(1/3)^n-0|

I'm doing a problem on magnetic force on a current carrying wire, and I'm wondering; if the velocity of the current carrying wire is significantly more than the electron drift velocity, what effect will that have?

Which is the link between electromagnetic forces and gravity?

Can anyone give me please the relational algebra for the following SQL query ?

SELECT DISTINCT customer-name
FROM loan L,borrower B
WHERE L.loan_number = B.loan_number AND ammount BETWEEN 10000 AND 20000

The database general view is this if it matters.

relative to the electron nothing is different. Relative to you, it's just a moving electric field so it produces a magnetic field.

>relative to the electron nothing is different
But why?

I hate your post.

try again

My bad, I don't know exactly what I did wrong but I guess I have to find the solution on my own. Thanks though my friend. I'll try next time to be more precise if that's the problem or anything.

I would like the relational algebra version of the following statement:

SELECT DISTINCT customer-name
FROM loan L,borrower B
WHERE L.loan_number = B.loan_number AND ammount BETWEEN 10000 AND 20000

Because it's moving at a constant velocity so it's an inertial frame of reference. If you were riding along with it it would feel like you're not moving at all.

What are centrifugal and centripetal components of acceleration and their respective effects?

Obviously.
But you've completely misunderstood the question; the magnetic field does not move with the wire.

if all galaxies have black holes in the middle why doesnt everything get sucked up

Why does everyone want to go to Mars so badly? Wouldn't it be better to put people on the moon in colonies instead of Mars?