/sci/ - Science & Math

Wow, it's actually been a while.

>>10321995
Show him the moving portals meme.

lol scales cant read lmao

scale will give you a number which is supposedly validation of the theory of everything but isn't decrypted yet. This is an open problem in modern hypercoblic quantum field theory and has a reward of up to $250,000 by the Committee of University of Zimbabwe.

>>10321995
the saturday morning funnies?

lol, .5kg of flies is like 50,000 flies... laughed good at this one.

what did Professor say?

>500 grams of flies

Assuming a closed jar it will be 1 kg.

>>10322014
>professor
you think this is taught at university?

>>10322015
how about a 500 gram helicopter hovering in the jar?

>>10321995
1.5

>>10322019
Still 1 kg, again assuming the jar is closed.

>>10322022
so where's the downward thrust force going then?

>>10322015
>>10322022
>t. Brainlet
https://www.youtube.com/watch?v=N0IGrSjcBZs

>>10322017
>I just spent 1.5 hours arguing with my phys professor...

nah doubt, but just stating what was said..

>What does the scale read?
|| ||||

>>10322042
>has never argued with his professors for hours

what the fuck do you even do in college?

>>10322047
>doesn't get it
IQ too high for jokes.

>>10322043
it's clearly
>| / | | | /

>>10322035
>drones are just big flies

downward thrust is being dispersed into the bottle as pressure on all the walls. The bottle will be slightly heavier, but only the proportion of that pressure that is exerted downward.

>flies can generate .5kg downforce thrust

>>10322065
if you have enough flies that weigh .5kg making them generate that much is trivial

>>10322062

>>10321995
https://www.youtube.com/watch?v=PmfRaUfTuKs

>>10322047
about to start my physics degree..
transferred out of engineering, why would u argue with a teacher? most of the lecturers i've had are quite competent in their field. id be stupid to challenge there response.

If you put yourself in a big (closed) box on a scale. The scale reads 300kg (you fat ass). You jump inside the box. The scale weighs.... I don't know you are in the box and can't read it.

>>10322094
lmao 2008 internet tier like the potatoe battery

>>10321995
it's 1.5kg

>>10322121

Its not 1.5kg you pig ignorant autard. Its 0.5kg because the flies are lifting the jar up by 0.5 kg.

1.0 - 0.5 = 0.5

Jesus fucking Christ, its that fucking simple!

>>10322064
>all those words and saying nothing lmao
>an x kg object needing less than x kg of thrust to hover

The correct answer is 1.

>>10321995
correct answer is .5...... lol idiouts

flies literally lift the jar up.. what do u think their doing otherwise? r u guys serious lmao...

>>10322152
through what mechanism do the flies gain lift

>>10321995

Listen you massive stupids, its a simple question, which only dull brained dimwits fuck up.

Okay, here is a BIG TIP. READ THE QUESTION. WHAT FUCKING INFORMATION ARE YOU GIVEN?

Oh! YES THAT'S RIGHT NUMBSKULLS!

the jar weighs 1.0 kg
the FLIES WEIGH 0.5 kg

Got that? No? oh, severely fucking retarded aren't you? Lets try the important bit again.

the flies WEIGH 0.5

Which means, regardless of whatever dumb assed assumptions you have made regarding the picture, the fact remains that the flies are exerting a force of 0.5kg on the scale.

THE FLIES WEIGH 0.5kg, other wise the scale would NOT register them as weighing 0.5kg in the first place!

It matters not a fuck what the hell the flies are actually doing, where they are, whether its a vacuum, whether they alive or dead, whether they are beating their wings, the force of the down draft, etc, since THE FLIES MAKE THE SCALES READ 0.5kg then the flies are exerting 0.5kg of force upon the fucking scale!

In other circumstances the flies MIGHT NOT weigh 0.5kg, BUT THAT IS NOT THE INFORMATION YOU WERE GIVEN.

YOU WERE TOLD THE FLIES WEIGH 0.5kg !

Have you got it yet? Has it sunk in? Has it finally passed through that virtually impenetrable cluster fuck of shit that you call your brain?

The answer then is a simple 1 + 0.5 = 1.5kg

Now if you cant see that, if you still dont understand, then if you have any love for your fellow human being, then never ever have children.

Now fuck off.

>weigh
>kg
I think you mean newtons, buddy.

>>10322209
Ugh ....sorry... I'll try being smarter...

>>10322209

>>10322205
By flapping their tiny little goddamn fly wings you retard

>>10322209
actually the important bit of information isn't even mentioned in wording: the fact that the jar has a lid on it. otherwise the fly would not be exerting .5kg of force onto the scale

also everyone here is trolling retard, i know because i made a quarter of these joking brainlet posts

>>10322216
k is the mass unit. The weight unit is k*g.

>>10322242
Cant tell if trolling again but it's still 1.5 even if the lid is off as long as the flies don't leave the jar.

If they're moving around in the jar, how the hell are you suppose to get an accurate measurement? The motion will just throw off the scale so it's literally impossible to weigh them. And if it's impossible to weigh them, does that mean they're in a state of quantum flux?

Could this be a Schrodinger's jar of flies?

The scale shows actually a force.
On the earth it’s about 14,72 N.

F = m x g = (1 + 0,5) kg x 9,81 ms^-2 = 14,72 N

>>10322209
wrong what if the flies were weighted on another scale
bazinga

>>10322209
>flies are exerting a force of 0.5kg on the scale.
lol brainlet mass aint no force

>>10322272
What kind of bullshit is this , and not a . learn to stop making your numbers look like shit

>>10322249
>it's still 1.5 even if the lid is off as long as the flies don't leave the jar.
nope if the container isn't sealed, then the air can escape into the environment without transferring its full downward force to the cage, and it will be lighter when the flies are flying

so 1.0 <= answer <= 1.5 if there were no lid

>>10322030
yeah exactly, the weight would vary depending on how many flies are thrusting their wings, frequency of flutter,

>>10321999
>Yeah .5 kg is like 50,000 flies
Found me

>>10322209
>the FLIES WEIGH 0.5 kg
they dont, actually the real answer is that the question lies to you.
The flies actually weigh 2 pounds. Thats the real trick. You need to be on my IQ to understand that. The info was there for you all along brainlet.

>>10322311
Be prepared for a mindfuck...
All „normal“ scales indicate the wrong unit. It‘s not kg, it‘s N!


Over time, it is on average 14,72 N!

>>10322015
>>10322022
>>10322314
>>10322209
>>10322182
>>10322152
Honestly /sci/ needs to implement a fucking randomized science exam BEFORE THESE RETARDS CAN POST BECAUSE THEY KEEP SHITTING UP MY GODAMN BOARD

>>10322209
After all these years this meme still delivers

>>10322314
>I'm dumb and don't know physics but still post on sci.
See >>10322035 and then kill yourself.
Alternatively if you are still trolling skip the video and just kill yourself.

>>10322367
No he's right. When the drone flew near the top of the box without a lid, the measured weight was slightly different since some air was deflected and carried momentum into the area outside the box. With precise enough scales, you'd probably be able to measure the change with a singe fly near the bottom of an open box.

>>10321995
1.5 - mass of air displaced by the walls of the jar and the flies

>>10321995
Assuming the pressure remains coming from constant, inside and outside, the contained pressure would act directly on the scale and would be no different to the flies "jumping" off the scale. Weight would increase when the flies pushed down and would decrease when they pushed up, because you cannot feasibly track all the flies (unless you had a scanning system) at the same time, you can get a constant on their average flutter variation and measure the weight change yourself.

>>10322069
I mean that's a fuckload of flies

>>10322356
jealous of anyone who gets to crime while driving, it seems really comfy.

>>10322466
The more flies, the higher chance of the weight remaining constant. However if they are in synchronization they could fluctuate between 1.5 and 0.5.

>>10322475
Yes, but WHY are the flies random?

>>10322474
just go to chicago in a 1995-2005 toyota, dump plates, and carry out all the crime-bys your heart desires

>>10322450
>I am so ignorant of physics I misunderstood what was happening on the video.
kill yourself

>>10322499
Then what was happening in the video? I see it as a textbook question on the conservation of momentum, plus the concept of impulse I guess.

>>10322504
When the drone got high he fucking turned down the thrust.

>>10322529
So why then, when the drone is higher than the box, the scales show -21

>>10322544
Because he turned the thrust off completely.

>>10322529
When the box was open? Compare this to the situation with the big drone and the glass plate. I'll admit he could have used a more stable drone.

>>10322546
So even if the drone was say, 10m above the box, it would still be reading 0?

>>10322551
Maybe >>>/x/ is more your speed if you cant understand this basic shit.

>>10322553
The drone isn't 10 meters above the box.

>>10322562
But lets say it was

>>10322573
Then the scale would read very close to 21 because the down draft(force) from the drone spreads and distributes vaguely in the shape of a cone.

>>10322573
>>10322592
Meant to attach image.

let's replace the flies with quadcopters

>>10322592
>>10322596
Surely, it will not read close to 21, because the scale is only small, and the cone (after 10m, or lets say 20m) will be large. Right?

>>10322597
Late to the party read the thread.
>>10322035

>>10322601
The higher up the drone the closer to 21 I don't know if you are trying to be stupid or don't know what a cone is but similar cones have increased area with increased height.

>>10322609
Sorry, Sorry, I forgot that the scale was zeroed.

My point is, the higher the drone, the closer to -21 it should be. Great, we agree.

So when the drone is fractionally above the box, the scale will be fractionally below zero. As the cone will be fractionally larger than the width of the box. Thus, you are wrong, and this poster is correct >>10322450

>>10322562
At one time in the experiment, the drone was providing thrust equal or greater to its own weight force while being above the edges of the box for perhaps a second starting at 2:58. If the scales updated more than once a second and was a dp more sensiti you'd probably see this reflected as a non-zero count on the scales.

Point 1:
The reason the scales show a deflection is because momentum is being carried in the air pushed down by the propellors of the drone in equilibrium and is transferred into the bottom of the box.
Point 2:
Vortices and sideways air currents carry some momentum away from the propellors of a drone in equilibrium, since they're not optimised to direct air solely in the downward direction.
Point 3:
A drone at equilibrium significantly above the box will impart momentum to some air in a direction such that it directly couples momentum downwards at an angle towards the ground but away from the box.
Point 4:
The air currents inside the box will transfer momentum to air above the box, which will transfer momentum to air outside the box, which will transfer momentum to the ground without impacting the scales, particularly if the drone is near the edge of the box. This process will be very inefficient, but noticeable with sensitive enough equipment.
Point 5:
When the drone is in equilibrium above the glass plate, some of the air is imparting momentum into the plate and some of it is imparting it to the ground directly, hence the measured weight being between 0 and the weight of the drone.

So which of these do you disagree with?

>>10322618
Do you know how a cone works?

>>10322623
Yes. That is not the correct answer to my post. I deleted it because I saw the error. It's nothing to do with the cone.

If another 0.5 kg of flies passes 5 miles above the setup with nothing else between them and the jar, what will the scale read as the extra flies pass?

>>10322621
If the area of the dowforce cone is entirely within the boundaries of the box the entirety of the force from the drone makes it into the box and the scale.

On the test with the full sized drone more than 80% of the weight got to the scale with no walls and more relative height than the small drone had to the box.

Do y'all really not know what a cone is?

>>10322625
>I deleted my post.
Weird how your autism doesn't make you smarter.

>>10322621
Why do a number of your points say the same thing in different ways? Do you like to add pointless words to sound superior?

>>10322641
Don't worry, he is just covering up the fact that he doesn't know what a cone is.

>>10322637
...and yet I am still smarter than you, as you think that when the drone is above the box it will still read 0.

>>10322064
So you have to account for all that downward thrust that doesn't thrust downward?

>>10322647
Look, people learn what cones are every day. Even I wasn't born knowing what a cone is. There's no shame in learning something new. You just gotta be honest with yourself.

this is my first time in this board and fuck im already in tears.

>>10322634
It's not like the drone is rocket-powered, there's air moving both below and above it. I suppose both would be roughly cone shaped. The point is, the air moving above the drone and down into the props is laminar flow, the definition of which means there's a velocity gradient going horizontally. Pic related, some momentum will be coupled outside of the box.

>>10322030
The downward thrust would add to it but the air would also hit the sides and top. This has only to do with the fact that the heli would be too close to the bottom. I think the force would dissipate within the "atmosphere" if the jar weighed the same but was huge. Never tried it, but I doubt you feel the force from a heli dozens of km up IRL

>>10322679
Nice 4 inch box to prove your tiny point.

>>10322685
It's a very small effect, and that case is the one to make it the most obvious, but it should still happen.

>>10322693
Not on a larger box where the drone is further from the walls. The effect is completely localized within the circle of rising air that leaves the high pressure at the bottom to fill the low pressure at the top. And would be negligible even in the case shown. Ask yourself if the drone were fixed to the wall how much exterior thrust you would get from this side effect.

>>10322005
Portals aren't real so arguing over their behavior is pointless.

>>10322700
False, the answer is B.

>>10322464
Brainlet. Only the closed jar contributes buoyant forces.

>>10322700
>Portals aren't real
Neither are spatial dimensions beyond three yet mathematicians jerk off to that shit all the time.

Is this a good time to point out that you don't "weigh" kilograms, since that's a unit of mass?

>>10322015
cringe

>>10322698
>completely localised
Are you familiar with how fucking large avogadro's number is?

>>10322714
Are you aware of what a circle is?

>>10321995
each of those flies masses 100 grams. That's pretty large. There is no known flying insect alive today that masses that much. So either the flies aren't flying or we have massive mutant flies.

>>10322716
It makes some intuitive sense that while some air is made to move downwards a la >>10322679 an equal amount is made to move upwards, hence cancelling everything out. But then how do you rationalise this such that there's a difference between the drone being inside the open box and above it, or being above a glass plate? How do you explain that this cancelling doesn't happen when the drone is high above an open box or a glass plate?

If this isn't what you were trying to say then you'll have to be more specific than "circles". Again, Avogadro's number is large that we can assume that even a millionth of a millionth of a chance means happening on the order of 100 billion times.

>>10322734
I can't tell if you are too smart or too dumb but.
>what is conservation of momentum?

>>10322740
Isn't conservation of momentum what I was arguing for in the first place? An atom with x speed collides into another atop, and they both leave the collsion with speeds y and z that add (vector wise) to x. The first atom is above the box, the second atom is above but next to the box, give or take a few million collisions in between.

>>10322005
>>10322700
>>10322702
>>10322706
The moving portals problem really isn't a physics problem because portals already violate the laws of physics: namely, the laws of conservation of energy (you can put portals at different heights and get free potential energy) and momentum (you can go in one portal facing one direction and exit the other facing the other, which would flip the sign on your direction and therefore your velocity and therefore your momentum). They're literal magic. Trying to figure out the physics of portals as presented in the games is like trying to figure out the physics of magic projectiles in Morrowind.
No. Literally all the problem requires is an understanding of how they work in game. Portals conserve the relative speed of whatever goes in; per GLaDOS, "Speedy thing goes in, speedy thing comes out." It's B because, relative to the portal, the cube has speed. You can't ask where's it getting that inertia or kinetic energy because the games have already established a lack of fucks in those regards.

>>10322743
>I am too smart to understand.
Ok, I can talk to you like an adult.

The only way that force is exiting the box is if some of the air with downward velocity is outside the walls of the box. in the case of a centered aircraft in or above a large box the downdraft creates a swirl of updraft in a ring around the aircraft as the air circulates with the air that hit the ground rushing sideways and eventually upward to fill the void above the blades. The downward velocity air is completely contained within the circular ring of upward moving air meaning that even when above the edge of the box if the air at the edges of the box all has an upward velocity then all the force is imparted on the box.

Jar weighs 1.0kg
Flies weigh 0.5kg, regardless of whatever they are doing

Total weight must therefore be...

1.5 kg

What do I win, apart from the "Replied to Retarded Thread" prize?

>>10322758
That's probably true. The case of a propellor (or array of propellors) the very middle of the box will mean there will be air travelling upwards at the edges and down at the middle, but in the case of an array of propellors all at the edge of the box the outside air will be moving downwards at the edges and up in the middle. So conceivably you could get a little bit more than 0 or a little bit less as measured by the scales.

>>10321995
1 kg cos the flies aren't applying pressure the the scale, and they aren't applying force to the scale. Also, this is a bit basic for uni doncha think

>>10322843
Then how do the flies stay in the air? Every reaction have an equal an opposite reaction. This is a bit basic for elementary school doncha think

>>10322845
Idk. This is bait anyway so whatever. Op is long gone i think

>>10322848
It isn't really bait, replace "flies" with "3 heavy drones" and increase the size of the jar.

>>10322852
Fair enough.

Okay retards,
For a theoretical fly motionless in midair the gravitational force is balanced by some thrust of flight. The air in the sealed jar experiences an equal but opposite reaction force. Since the jar is sealed, the air mass does not move and this force is transmitted to the walls of the jar. Assuming the jar does not move (not necessarily a safe assumption as the mass of the flies approaches the mass of the jar...), this force is transmitted to the scale. (A small amount of energy may be dissipated as heat as the air circulates.)

>>10321995
God you people are retarded. It doesn't say the flies are FLYING so they're clearly clinging to the jar, hence it's 1.5kg.

>>10322870

....and you dont give an answer, you massive autarded piece of pig shit.

>>10322886

it doesn't say they are clinging to the sides either you inbred hick.

>>10322893
That's true. They could be clinging to the base or the lid, but it's still 1.5kg

>>10322888
the answer is quite plainly there, you massive autarded piece of shit. at equilibrium (no net momentum) the scale reads 1.5 kilograms, assuming the other factors I mentioned are negligible

>>10322751
Good answer, but I still think A is the case. The cube has zero speed as it goes into the portal and whatever magic portals do to the object happens once the entire object has entered the portal as evidenced by gravity shifting in the games only after you have gone through entirely. Try it out with the smashy things in portal 2

You're all fucking stupid. Noöne told that all the flies are flying at any instant. So the answer has to be independent of the number of flies flying, so it has to hold even when no fly is flying. Thus it's obvious that the scale reads 1.5kg.

>>10322014
>0.5kg of flies is like 50,000 flies.
You think a fly weighs 0.01 gram?

>>10321995
Step 1: imagine the flies sitting on the bottom. What does the scale read?
Step 2: kys

>>10322923
It's probably closer to 20mg, but yeah that's about right. Google it.

>>10322934
That is about 10 times less than I expected. Learn something every day.

>>10321995
In order to be flying, the flies needs to push down an amount of force which equals it's own weight.

If you can ignore air resistance/the air which is being pushed downwards in chaotic direction and just assume that it goes straight down, the answer is 1.5 kg

>>10322937
It's because the mass decreases as a function of the cube of the length, so a 3mmx3mmx3mm cube of water will weigh 27mg. Expecting it to be closer to 6mm^3 is understandable however, but there really isn't as much water in them as you'd expect, likely thanks to some sort of highly porous (and crunchy) exoskeleton. Makes you wonder how a capillary the size of a human hair is supposed to function.

>>10322947
Read the thread, nobody is arguing that anymore.

>>10321995
>stand below a helicopter which is landing
>suddenly get squashed by the downward force which is equal to the mass * gravity of the helicopter, as if the helicopter physically landed on my head

>>10321995
Those are some big fucking flies, but anyway, they won’t contribute to the weight of the jar unless they land, because they’re generating lift to negate the pull of gravity on their bodies.

>>10322954
AKSHUALLY, if the helicopter is landing, then the force is less than the mass times gravity.

>>10322064
If you don’t know what conservation of momentum is, you should have to retake the previous class

1kg, the flies are in the air, so only the jar is weighed correctly.

>>10322962
Not if it's velocity is already constant downwards

>>10322954
No, you'd get squashed by the equivalent force for your area at that downward pressure. If it's hovering at 3m, it will have a cone diameter of perhaps 26m (assuming helicopter length of 16m), so the area will be 530m^2. It's mass is perhaps 5 tonnes, hence having a weight force of 49kN, making a downwards wind pressure of 92Pa. Assuming an area of around 0.6m*0.2m = 0.12m^2, that's a force of 11N, or about the equivalent of 1.1kg of mass on your head and shoulders. Sounds perfectly reasonable to me.

Why doesn't the thrust the flies generate disperse? Does all the air molecules hit the bottom of the jar?

2kg because the flies must also generate 0.5kg of downward force. Go back to pre-school, brainlets.

>>10322908
>zero speed as it enters the portal
Relative to the portal, it has speed.

>>10322626
Not if they're inside a jar.

>>10321995
a little bit more than 1kg, the higher the flies are the more the force of the flapping wings is exerted on the sides and not the scale.

>>10322047
>argued with his professors for hours
>hours

No respectable professor would ever give that amount of time to a student, you're full of shit!

>>10322848
>OP is long gone anyways

I'm right here in the bus waiting to get to my physics class. I was supposed to be armed with an answer and explanation by this point..

>>10323000
>Be me sitting at home
>Flyover state
>Read this post
>Suddenly hear a roaring
>Ground shaking
>Step outside
>Airplane
>Flying straight for my house
>Mass from airplane being suspended crushes everything underneath
>House gets fucking destroyed due to newtons 3rd law

Mkay retard

Daily reminder that among the trolls there are some genuine brainlets who can't solve this.

>>10323922
Try the same plane buzzing a few feet over your head instead of a thousand and you'd absolutely feel the effect of the displaced air.

>>10322011
top kek

>>10322209
include me in the screencap

>>10323932
That wouldn’t work either you dumbass because planes generate thrust differently from helicopters

>>10323910
Maybe if you are a brainlet they don't

kek, it's basic third law of dynamics. OP is retarded.

>>10321995
>10322047
There's too many confounding variables like how many flies are in the air versus what's on the jar at any given moment. I believe the scale will fluctuate.

What if you have a big 1 cubic meter jar (let's assume it weighs 10 kg) filled with exactly 1.225 kg of air? What does the scale read now? 11.225?

>>10324049
If you zero and measure it in a vacuum, that's exactly what it will read

>>10323821
That doesn't matter. Portals are magic, remember? The important thing is that gravity does not affect your sprite until you have gone completely through the portal

>>10322367
>I'm dumb and don't know physics but still post on sci.
that doesn't even make sense as this isn't an exclusively physics board and the video you pointed to only proved me right

what if i told you the scale would oscillate on a (number of flies) phase sine-wave that hovers around (weight of jar) to (weight of flies + gravity)

>>10321995
1.5kg if it is air tight.

>internet version of truck with pigeons.

The flies aren't exerting any force onto the scale, therefore 1kg. Scales measure weight, not mass.

>birds in a truck

>tfw a plane flies overhead and you weight 2000 lbs on the scale

Haha! The dummies in this thread!

Its simple, when you look at the flies you will collapse their probabilistic wave function. They will then become either dead or alive. Dead flies weigh less than living flies because they no longer have souls.

>>10321995
Depends on which, if any, astronomical body.

>>10323932
I don't see jar height as a fixed variable, so the test taker gets to choose. I choose a really spacious jar.

pic related is a magnet levitating above a superconductor. assume the magnet weights 1kg and the superconductor weighs 10kg. what if i put it on a scale?

>>10324766
fuck, forgot pic

>>10323922
The cone (>>10322596) from a fixed-wing aircraft of all things would probably be more than a kilometre wide. But even a helicopter hovering an inch above your house probably wouldn't be enough to crush it, you'd only have a total pressure of perhaps a few hundred Pa, which is less than the force a heavy rain would apply. Roofs are made to take a lot of downwards force, especially in an area where it snows. Dry, third-world places probably are more in danger of helicopter damage due to the lack of rainfall and lack of strict building regulations.

>>10323961
Planes can make use of the ground effect (see caspian sea monster) but you'd have to be at the tailing end of the wing and very close to it. I've never driven a convertible directly behind and under a landing aircraft so I couldn't tell you how much you'd be able to feel it, but it wouldn't be that much.

Anyhow, here's another thought experiment: You have an open box on a set of scales and you fill it with 10L of water. You then suspend from the ceiling on a piece of string a metal ball with a volume of 1L and mass of 10kg. Assuming the box itself's mass is negligible, what weight do the scales display?

>>10324766
11kg

>>10324777
11 kg, right? the buoyancy force of the water on the ball is that of the 1 liter it displaces

>>10324807
Basically, yeah. It can be a good method of measuring the density of something if collecting the overflowing water is too difficult, provided the string is small enough.

>>10322679
conservation of momentum disagrees with your pic

>>10322343
underrated

>>10324883
Not in the slightest. If so, then a drone high above an open box would have no mass change compared to a drone in a closed box. Regardless of where the momentum is coupled, whether it be inside or outside the box, the drone can still maintain a steady state, see >>10322743, >>10322832.

>>10322621
That's physics beauty right there. I love you anon

>>10324131
I don't exactly see how that's relevant.
Just consider how it looks midway through the event. If the portal is coming down on the portal at speed |v|, then it makes sense that the cube would be emerging from the second portal at the speed |v| as well. What is the alternative? There is lag between the cube entering the first portal and emerging from the second?

>>10325538
It's a pretty awful question because portals don't conserve momentum. Considering all reference frames, I think the portal should shoot out the second portal with velocity relative to it, and anyone that argues conservation of momentum or energy should be ignored. But trying to imagine what happens if you're halfway through the portal and it starts accelerating back in the other direction and you've a recipe for confusion. I can only assume that one half of your body is affected by gravity on one side of the portal, and the other half is affected by gravity on the other side, so you'd get a net force in one direction or another.

>>10322103
>arguing from a place of competency
You’re supposed to argue constantly everything the professor says until they can convince you
I don’t even use the textbook. I just show up to lectures and contradict everything the professors says then ask if they can explain why what they’re saying is true

>>10321995
For every action there is an equal and opposite reaction
In order for .5kg of flies to be lifted in the air, they must push down (the air) with .5kg of force
Assuming the jar is air tight, their weight is being transferred to the bottom of the jar through the air
There is no way to change the weight of a closed container using only things from within
Anyone with basic layman's knowledge of physics should be able to figure this out.

>>10325935
Implications are fascinating, fly in bubble in 0 gravity can move whole bubble but Musk is retard who's using rockets to get to Mars.

>>10325935
Air is pushed down. Flies create immersive low pressure at top of a jar and big pressure at the bottom and jar is going to explode and implode at the same time!

>>10325935
>air doesn't circulate if there are no flies
>the flies literally push down all the air
>trying to act smug while in reality he cannot into aerodynamics
just...

>>10322035
This is a shitty (((experiment))).
The drone and the container should've been weighted seperately. Then the drone should've been put in the container, the container should've been sealed and then the whole thing shoul've been put on the weight; In that order.

>>10326078
*and the whole time inbetween the container being sealed and being placed on the weight, the drone should've been flying without touching any sides of the container.

>>10326081
Drone works differently than a fly.

>>10325592
>It's a pretty awful question because portals don't conserve momentum
they literally do though, that's how they're coded in the games. there's a physics bubble hardcoded around each portal and any momentum the object had going into one portal, it keeps going out

>imagine a fish bowl full of water
>put gold fish into the water, does it weigh more with the added goldfish?
Air has weight too

>>10326705
Wrong. If you have one portal facing upwards and another facing sideways, by jumping through that portal you're not conserving the total vector momentum of the system. You can't deflect an object to travel a different direction without feeling some force on the reflector. It's never been canonically demonstrated that such a force isn't present on the portal bearing surfaces, but since we see portals being placed on some fairly flimsy surfaces without wobbling I think it's a fair estimation.

As far as conservation of energy goes, it utterly destroys the concept of a conservative field.

>>10321995
Unambiguously 1.5 kg :^)

>>10322751
Post the problem pls

Stand on scales and weigh self.
Now jump
What does scales say while you are in the air?
Or just your body displace your weight in air in the room you in and maintain your weight on the scales?

>>10321999
>how can 5 flies weigh 0.5 kg
I feel it

>>10321995
Why does it feel good when I make someone put their peepee up my butt?

IF the flies are flying, in a closed system (lid closed), the scales would read 1.5kg. The flies have to exert a force equal to their own weight to prevent themselves from falling.

>>10327711
>a body in free fall is analogous to a fly exerting downward thrust

>>10327704

>>10327819
What makes think they arent falling?

>>10327832
I assumed the flies are flying. If they are flying, they are not falling and thus exert thrust. What kind of autist sees the drawing in OP and thinks the insects are in free fall

>>10321995
Those flies are very fat

>>10327849
>I am the first person to have ever thought of this

>>10322322
>>10322684

holy fuck the only valuable posts in the thread and neither have a (you)

Here you go anons.

>>10326078
>I'm dumb.
>>10326081
>I'm dumb and autistic.
We get it.

>>10322011
sponsored by a Nigerian Prince, I believe

>>10321995
1 + (0.5×5) = 3.5kg

By flying you are essentially making the force from the pressure immediately beneath you be greater than your weight force and the force from the pressure above you. Even with the jar completely sealed, the average force of molecules bouncing on the bottom part of the jar will be greater than those bouncing on the jar's cieling by exactly your weight. This is because of the particles accelerated downwards by the fly's wings.
In the case of the jar floating in space, the flies gain in momentum towards any direction could be seen as the jar moving now into the oposite direction. Until the fly crashes into the other wall and the momentum is completely cancelled.

>>10327837
What if they're freefalling but at terminal velocity? Then I think the scales will read 1.5kg.

>>10327711

If the flies were in the process of jumping then they would weigh 0.0 kg.

However the information given in the problem says the flies weigh 0.5kg YOU IMMENSELY STUPID PIG FUCK!

>>10323910
Last semester, I made an appointment with one of my philosophy professors to talk about a paper and we ended up having a two hour conversation about the philosophy of abortion (totally unrelated to the course). My ugrad thesis professor (chemistry) and I had an hour long discussion comparing his experience with censorship in Soviet Russia to the Charlottesville protests.

I'm not saying it happens all the time but it does happen. Undergrads and professors are both people, there's nothing stopping them from clicking and starting friendships.

>>10321995
Thrust of flies is generated from fluid friction forces which would not directly translate to the scale (where are you people getting 100% efficient motion transfer through fluids).

Not to mention the reality that at any moment they could stop flapping and be in momentary free-fall.

>>10322700
>portals arent real
Citation needed

>>10321995
Question lacks information to be answered. What does the scale read when? When is the observation taking place? The flies aren't magically just hovering, so maybe they land, maybe they are in flight. Maybe the eventual "equilibrium" of the jar/fly system is for all flies to be at rest, landed on the inside of the jar. Thus, 1.5 kg. Otherwise, the correct answer is an estimate of probability, where a certain probability function is applied over a the possible scale readings (1-1.5).

>>10321995
Lookout, mechanical engineer coming through.

The flies are flying because they are moving air downwards.
Assuming fly velocity is constant, the the force of the air on the scale would cause it to read 1.5 kg.

Taking into account viscous damping, heat production, noise production effects, it would read less than 1.5 kg due to lost energy.

>>10329189
I think it depends on the diameter of the cylinder that the mass is pushing on. You fucker.

>>10321995
keek

>>10322209
You're literally wrong and proved you're retarded, do you have literally zero understanding of how physics work in a VACUUM? The answer is obviously 1.0kg because the flies are suspended in a VACUUM. There's plenty of literature available regarding physics in vacuums. Look at the space shuttle for example, the force they (the crew) exert while suspended in "open air" of the ISS doesn't sway the ship with the proportional amount of force they are exerting on the air surrounding them. It is marginal at best and still not even a fraction of the actual force in weight in mass by shifted, the air absorbs the force if they are waving their arms around. That ship won't start rocking like a low rider. This board get stupider by the year with newfags like you serious. My PhD is probably older than you at this point.
For safe measure, I'm going to give you the warning: you have to be 18 years or older to post here, sweetie.

>>10329195
Flies flying upwards will lead the jar to weigh more, flies flying downwards would lead the jar to weigh less, and flies in steady-state would cause it to weigh 1.5kg. With as many as 50,000 flies we can average the total vertical fly-flux to remain at 0, hence the change in fly flux will remain at 0, therefore the fly force on the scales will remain at the constant 0.5kg*9.81. Hence the scales will always display 1.5kg.

The answer is 1.5. Correct or not, I'll be the one who Ace the test because that's what any professor would want you to answer. How is it that difficult for people to know the answer lies in what the professor will deem as correct?

>>10327829
Obviously A

>>10329734

Damn, this go so many replies I can;t be arsed to see if anybody has suggested you counter with pic related.

A jar and lid weigh 1kg when weighed sitting next to each other. If you put the lid on the jar, does the air inside suddenly make them weigh more?

If the flies are flying around inside the jar with the lid UNDER the jar, and the jar thus open to the air, does their weight show on the scale? Does it suddenly show on the scale if you move the lid to he top of the jar?

>>10322069

I won't go into details, but I know this to be true from experience.

>>10329309

under rated.

>>10329294

Fite me!

1 vs 1 in the wilderness now!

>>10329782
>will it take off
No, it will hit the legs of the control panel and stop.

>>10330379

Not if its in a vacuum. In which case it will rise straight up.

>>10321995
1.

Even if there was differential air pressure (and air pressure would be virtually the same inside the jar), it is only a force applied to a jar. Try touching an air horn or compressed helium jar. It doesn’t push you away any more than a decompressed airhorn or helium jar. Try pointing a fan at a wall and then go to the other side. The fan isn’t pushing you.

If this was possible spaceships would have an airtight container and a fan for infinite thrust. But the fan can only induce rotations, it doesn’t create thrust.

>>10329294
If the flies are in a vacuum and unmoving, then they have to be under some other force in order to not succumb to the force of gravity. If this force is a conventional thruster of some kind, then this engine's exhaust will carry momentum onto the box and the scales will show 1.5kg. But it's conceivable that the flies are being kept in place with an external force like a magnetic field, or that the flies are using photon thrusters that pass through the box without transferring momentum to it, in which case the scales will show 1.0kg. Without stating how the flies are suspended in a vacuum it's hard to answer the question.

But if you have 50kg of astronaut in a 100kg space station, pushing himself about by the air will show the space station itself moving significantly in the opposite direction as the centre of mass remains in the same position. Your ISS example does absolutely nothing to help your example, as the ISS is simply in microgravity, the people inside it aren't in a vacuum at all. In addition, the "marginal swaying of the ship" that you write into obscurity is highly significant in a case where the contained object(s) total to half the mass of the container and displays the conservation of momentum that's essential to understanding this question in its standard format.

>>10323894
Upvoted!!!! XD Can I add you to my 4chan friends list? I really like your username!

>>10327829

>>10332869
It depends of the transferance of the box atom by atom would force the box to move faster out of the portal to allow for more space to move the next layer of atoms through. From the game mechanics this doesn't seem to be the case, therefore, as strange as it looks in your gif, it is scenario A.

>>10321995
physics undergrad here, being as wise as i am, i wil assist you peasants. *AHEM*.

Let us smash the flies so they are dead. They fall on the scale and the final reading is 1.5 kg. Now let us revive the flies and choose to assume they hover some distance z>0. The downward force from their wings is dispersed not just in one direction so the probability of an air molecule being affected by the wings and hit against the scale (resulting in pressure, resulting in a force applied) is very small. The scale will read 1kg.

>>10332869
lmao ez momentum conservation. B is correct

>>10332913
retard

>>10332869
If the portal only came half way down, then if B was correct the top of the box would drag the rest of it through, almost like it's getting sucked through

>>10332918
ok let me help you out. no one knows the science of portals but there must be some interacting medium between the "hole" of the portal and the object. this is a collision problem and the momentum of the portal must go somewhere.
>imagine playing the game portal and thinking you know anything about anything
retard

>>10332869
B but the velocity is gained from the two platforms. If the box were sitting on a scale the scale would read an increase in force as the box is traveling through the portal. This subtly slows down the moving piston and is where the force comes from.

>>10332869
Neither because you can't place portals on moving objects

>>10332962
https://www.youtube.com/watch?v=mCQiwhik8nc

>>10322152
>someone actually fell for this shit bait
And I thought I was a newfag

>>10332998
Ok lets just fukken do this in Garrys Mod and see what happens

>>10333056
Already done the physics only works on stationary walls and in that one game sequence.
https://www.youtube.com/watch?v=S85nudR6D-Y

This problem is unsolvable without making a few assumptions.

If the flies are flying and all in the air as seen in the picture. Then only the weight of the jar should show up on the scale. So 1 kg.

If the flies are dead and making contact with the bottom of the jar, then the weight of the jar plus the weight of the flies should appear on the scale. 1.5kg.

If the flies are pushing against the top of the jar from inside. The jar will either not make contact with the scale(it will be lifted up) and thus the weight is unknown.

Or if the jar is being pushed against by the flies, but not breaking contact with the scale, it will be the weight of the jar minus the weight of the flies. 0.5kg.

Its all about how the flies are making contact with the jar, otherwise it is unsolvable because there is not enough information.

>>10333237
So you’re telling me an ISS astronaut can push his space station into a different orbit?

Does anyone have the one with the balls submerged in water held by a string?
I never really got that one either.

If the flies aren't flying then obviously it's 1,5
If they are then the force they need to generate upwards is probably transferred downwards onto the bottom through the air so stil 1,5

Scales measure the force applied to them, not the actual mass of the object

>>10322103
They're confident in their field, yeah, but sometime profs say stupid stuff, like that one time my prof argued that the human ear can't perceive differences in pitch smaller than 24 hz.

>>10333464
Yeah, that's a thing. But at some point they're gonna hit a wall and cancel whatever acceleration they gave to the ISS.

Each little push changes things a little bit, but all the little pushes cancel out because the astronaut is confined to the station.

>>10333646
The center of mass doesn’t move.

>>10333985
Or I should say the center of mass of the astronaut and the space station keeps its course. Again if you were right there would be satellites moving fluid and rotating into a high orbit. But the CoM of the vehicle & free floating object / fluid will retain its orbital trajectory.

>>10321995
1 Kg

>>10322367
Just out of curiosity, why would you tell someone to kill themselves? What if they actually did it?

>>10334199
Hello newfriend!

>>10330379

https://m.youtube.com/watch?v=N0IGrSjcBZs

Drone in a jar

>>10334381
Yes it will
Take enough barfbags though

>>10334199
Noone ever agrees online. The natural response to any enticement from random people online is a rebellious "no, fuck you", worst case a passive aggressive "maybe i will!!" which will result in nothing at all as well. It's the desperately truthful, and broken, way of suicide watch, when people realize they can't really suicide, the might even try living.

>>10334734
Kill yourself

>>10334775
fuck you

>>10332935
the momentum of the portal is not relevant to the box

just think of it as a doorway, if an open doorway came flying at you and you stood still, would you suddenly fly forward with the force of 1000 suns or would the doorway just breeze past you?

>serious sci questions get 5 replies
>meme thread gets almost 300

i hate this board

>>10332929
And if B weren't correct then it would've collided with itself already before that point.

>>10334807
Both sides of a doorway can't move separately. If they could, and if one side were standing still, and you must still by necessity come out of one end of the door as quickly as you entered the other, it naturally entails B.

So yes, portals are indeed doorways, but you have to realise what that means.

>>10330914
>or that the flies are using photon thrusters that pass through the box without transferring momentum to it, in which case the scales will show 1.0kg.

After passing through the clear box, though, won't the photons hit the scale?

>>10332998
>Portal 2 is canonical.

GTFO

Assuming that the flies are an ideal gas and thus move randomly enough for their wing flaps and collisions with the jar to cancel out, and assuming that the weight of the air inside the jar is taken into account with the jars weight, how'd this go? 1.5?

>>10332869
Scenario A if you drop it in open space, B in a closed space

>>10335586
why?

>>10321995
OK, /sci/ get your brains out, here's a hard one.

>>10335641
I don't know enough about physics to come up with a convincingly bullshit reason why it should.

>>10335641
Assuming you have included an oxygen source to the torch, the gasses escaping the balloon out of the opening at the bottom should create some downward thrust. I don't know enough to say whether that thrust will be enough to lift the balloon unfortunately.

>>10335882
This seems like a good answer, I agree with this anon

>>10325935
>There is no way to change the weight of a closed container using only things from within
But that is exactly how the weight changes when I put stuff into the jar

>>10335393
Not if the scale is also clear, or of the photon thrusters are aimed downwards at an angle not to hit it.

>>10335882
Only if the burner is inside the envelope, otherwise the thrust it makes will go to either side and bounce off both the envelope and basket almost equally. You have to use the envelope itself as an engine bell, which is an interesting concept.

>>10336526
>You have to use the envelope itself as an engine bell, which is an interesting concept.

So hot air balloons on the moon would have the burner inside ant the basket on top.

>>10336533
Not really a hot air balloon anymore at that point, plus the envelope would quickly melt.

>>10322242
>actually the important bit of information isn't even mentioned in wording: the fact that the jar has a lid on it. otherwise the fly would not be exerting .5kg of force onto the scale

Also the flies would leave.

>>10335641
Yes because that is a movie stage in Hollywood.

>>10322030
if a plane is flying over you while you're standing on a scale that wont impact the reading though, right? The object is at rest in the air, through it's wings it's counteracting the downwards force

Why isn't it 1.25, or are there hidden flies?

>>10336544
what if the burner was replaced with 0.5kg of flies

>>10336750
Flies with photon thrusters?

>>10336778
the photon thrusters power the flies wings up and down

>>10336789
marvelous

>>10321995
Here's how I see this.
Since flies weigh 0.5kg, they need to put force of 5N, to stay in midair (F=m*a, where 'a' is the opposite of gravity, so 5N=0.5kg*10m/s2 (gravity simplified)).
Pic rel. Force that keeps the flies from falling (5N) goes into the air, below them. (F1)
Part of the force gets absorbed by the bottom of the jar, adding weigh to it. (F2)
The rest is reflected up, making it so that the air in the jar is in circulation. (F3 and second drawing).
That would make the total weight of 1kg + F2/(10m/s2), so something between 1kg and 1.5kg.

>>10336789
OK, let's not get silly, /sci/entists.

Maybe we should do some CFD to compute the force exerted by 500g of flies? Let's average out the wing flaps so at any given time half of them are flapping downward at once. Let's assume that each fly is a perfect sphere with no legs, and that the flies are perfectly stationary, and evenly spaced throughout the jar. A fly weighs 12mg according to some physics forum, so that's 20,833 flies (wow!) I can't really tell by the picture but it looks as if the top is open? So we have 20,833 flies weighing 12mg each, all flapping down at the same time. They are perfect spheres of let's say 6mm radius, with wings that are 7mm each in length. Someone needs to find the relevant geometry of the wings, and how fast the wings flap. We position them evenly around the jar... but we don't know how big the jar is!

New plan, we shall estimate the 20,833 flies as one MASSIVE BEHEMOTH MONSTER fly. It shall have a mass of 250g, a spherical body the volume of which will be centred in the jar and be equivalent to all of the small flies combined. It's wings shall be the equivalent of the total wing surface area of the smaller flies. It may steal your wallet, but it WILL flap downwards to sustain itself. We will assume it has wing-bones of carbon fibre so that the wings don't snap in half.

Can someone continue this work? I think there might be a research grant in it.

>>10336925
Each action has an equal and opposite reaction, so F2 would be identical in size to the difference between F1 and F3. Conservation of momentum is an easier way to approach this question.

The flies + bottle is an object with 1.5kg mass. There are no relevant external forces except gravity and the reaction of the scale. There is no movement of matter into or out of the bottle. The object is not accelerating on average, so the forces must balance on average. The reaction force must be 9.8 * 1.5N. The scale must read 1.5kg. There will be some fluctuations due to the flies flopping around.

>>10321995
weight and mass are different things; I've always sucked at physics and I knew this before I even took a course. he's probably right about you. assuming the flies aren't dead (as how they are represented in the image) and that the scale is accurate to within 10 grams, 1.25 kg ± 0.25 kg is the simplest estimate.

>>10321999
>How can 5 flies weigh 0.5kg?
This guy is correct

>>10321995
The only answer that makes sense is the average weight which would be 1.5 kg.

If the flies are in free fall the scale would show a minimum of 1 kg.

When they land it could go above 1.5 kg for an instant, hard to estimate what force they could hit the bottom with.

Likewise if they impact the top of the jar the weight could go below 1kg for an instant. Likewise, hard to estimate without more information.

Only answer that makes sense is 1.5kg (assuming no net acceleration on the group of flies)

If the jar is closed, the air inside the jar becomes a closed system and the .5 kg - lmao - force will be cancelled out and the jar will weigh 1kg, if it is open and they dont just fly the fuck out it would be a fluctuation between 1kg to 1.5 kg

>>10338628
lets say the lid weighs 0.1kg
would you have to lift 0.1kg or 0.6kg to take the lid off?

>>10321995
None. You're forgetting the mass of the air inside the jar. It should read 1.5kg + mass of air inside jar. The weight shouldn't matter if you weigh them separately or together.

>>10329782
No it won't. The wings will remain stationary relative to the ambient air so no lift force will be generated

>>10321995
369 kiloinches

>>10321995
Air has weight. Flies have weight. It would weigh 1.5 kg.

>>10341560
Actually, jar + air = 1 kg. In that case, 1 kg - jar = air.

>>10342842
good banter
tell me how much one m3 of air in Earth's atmosphere weights (at 100m above sea level)

Pascal would turn in his grave after reading this thread.

>>10321995
1.5 if the jar is air sealed
1 if the jar is open

>>10343547
>what is netwon's third law?

The mass within that jar is 1.5 kg
But the scale wouldn't necessary show that, the thrust from the wings affects the scale but the mass inside the jar is still the same despite air moving around.

>>10327829
I made this some time ago.

>>10343917
>hula hop
Also consider the portal slowing down while the box is still halfway though it, as this is where shit gets wierd. Arguably, as the portal surface impacts the box's platform, the box is still within the portal. So consider the case where the portal platform stops while the box is halfway through, or a quarter of the way through, etc.