/sci/ - Science & Math

>>11469000
tldr

>>11469000
What does the air in the jar weigh?

>>11469000
if that was water in the jar, instead of air, then the answer is completely obvious to us. use your brain. 1.5 is the correct answer

0.5 , because the flies "lift" the jar

Scales can't read!

fat ass flies

>>11469000
1.5kg, because that's how the metric system works-black magic and sorcery

1.5kg if the jar is sealed. Flies still supply a downward force when they fly

>>11469000
1.5 kg because it's a closed system

>>11469286
>>11469296
>>11469303
>>11469062
>1.5
brainlet

>>11469000
1kg (actually slightly more than that) because the force that the flies generate will not just push the jar downwards but also upwards and sideways equally as the air will swirl around the jar. The air dynamics will become pretty much constant at one point and the weight will hover right above 1kg, what will not be constant on the other hand is the heat generated by the motion

Checked

The flies exert no force on the scale

>>11469552
this

1.5kg. The flies must provide 0.5kg * g. of thrust upwards to stay afloat.

Consider a propeller enclosed in the jar. You should know that it won’t go anywhere if the propeller spins. Well, it will rotate due to conservation of angular momentum. But an enclose propeller will not lift the jar.

>>11471334
the flies exert force on the air, the air exerts force on the jar, the jar exerts force on the scale

Really wish people who've never had a physics course would stay away from problems like this.
>>11469552
Correct
>>11471450
The downward thrust they create is not constant in the entire jar. Hence why a plane doesnt push you to the ground when it passes you. In addition, the thrust created by the flies is diagonal, not vertical, so thrust is lost there as well.

>>11471467
I hate to break it to you, but you are an idiot.

>>11471508
Good argument pseud

The thrust should be equal or greater to the mass of the body of the ant plus air. Think of the flies not flying but chilling at the bottom of the jar. 1.0KG + 0.5KG = 1.5KG

>>11471772
brainlet

I think i got the right answer?

>>11471957
Kek , thanks anon.

>>11469000
Depends, was the jar put on the scale first, then the flys added later? Are the flies airborne during the measurement or grounded? Far to many loopholes.

>>11469000
i agree it depends..... is the top of the jar actually blue? if so then no, the top of the jar has to be green

Y'all gay. If the flies are never touch the bottom, they are not applying any direct force to the weighing scale, and as a result aren't counted as part of the weighed mass.

HOWEVER, if the flies are 0.5 kg each, they must be generating a lot of lift by pushing air mass down to actually be in continuous flight. The force that that flapping movement provides would be counted as part of the weighing. I don't exactly know how much lift, that's for one of you aerofags to figure out.

>>11469000

lol

also heres the answer for the 1.5kg posters.

imagine the fly is at the top of the jar pushing up on the lid. the down force on the jar is balanced by the fly pushing up on the lid hence the only thing the air contributes to is either stretching the jar a bit or creating air currents in the jar.

>>11472017
>the down force on the jar is balanced by the fly pushing up on the lid
It isn't. The downward force of the air on the jar from the wing flaps is greater than the upward force on the lid by an amount equal to the weight of the flies.
You can see this is true by imagining the flies are at the top, but flap just barely enough to maintain altitude. No upward force is exerted on the lid, but there is a downward force on the jar equal to the weight of the flies.

>>11469552
>>11471467
>>11471992
>>11472017
The AMAZING SEALED JAR that can decrease its mass depending on what happens inside.
kek, retards.
It will obviously always weigh the weight of the jar plus its contents.

>>11472098
its sealed with the same air pressure as the outside. take the lid off and its the same thing anyway. it depends how close the fly is to the bottom of the jar, too high up and the air will absorb all the kinetic energy as pressure differential.

>>11472115
There's no need to get involved with air pressure at all to answer this question. The power of Newton's laws is that you can definitively say, by simple conservation of momentum, that the weight of the jar on the scale must average at 1.5 kg if the jar does not accelerate. The finer details of air pressure and fluid dynamics cannot change this fact, they only give insight into how the forces are transmitted.

Do they not teach free body diagrams in high school anymore?

>>11469000
1 kg

somewhere between 1 and 1.5 because not all of the air movement created by the flies is going back to the jar and the still air in the jar is absorbing some of that air movement created by the wings of the fly.
think of inertia

>>11472098
Weight! = mass you mong

>>11472098
Weight =/= Mass

>>11472132
This

>>11469000
The weight of the scale will vary based on when the flies bat their wings.
It will be somewhere between 1-1.5 at all times

Just like a helicopter exerts downward pressure on a surface so will the flies

>muh air pressures
>muh differentials
>muh woogy boogy foogy forces

Its a closed system you retarded cunts

>>11472098
the force/energy isn't lost. the part that gets pushed against the walls instead of the bottom of the jar gets transferred to the air outside which has to push back against the outer walls of the jar. if the entire planet was one massive scale and no air was lost to space, then you would read 1.5 kg. as the scale is only under the jar though, not all of the force of the flies will push against the scale.

>>11472290
no its not >>11472132
energy is being dissipated to the rest of the planet.

>>11472291
absolute retard

>>11472298
when a helicopter flies over you, you don't feel a literal metric ton of force suddenly flatten you, do you?

>>11472299
You fucking brainlet, the air displaced by a helicopter in an enclosed space doesn't magically disappear. The particles of air are there and they weigh the same. No amount of fucking movement in the sealed jar is going to magically change the net weight of its contents. Go back and learn high school physics.

>be inside closed elevator
>jump up
>elevator raises slightly
>land
>elevator dips slightly
high school physics closed system fags BTFO

>>11469000
1.25g obviously. jesus you guys are fucking dumb as fuck

>>11472306
The elevator system system is not the metal box alone you mong.

>>11472305
this board is 18+

>>11472312
Yeah, so stay off until you graduate high school.

>>11472305
You'd be right if all the flies were just hovering in place (even then, particles are still hitting the side of the jar) but we both know that never happens. Part of the the pressure their flying exerts hits the side of the jar.
The weight is <1.5kg

>>11472311
the elevator is a closed box, just like the jar. instead of the scale being pushed up and down, you can measure weight by looking at how far up and down the cables are. neither is a closed system. their weights can change. weight =/= mass. mass doesn't change. low IQ retard.

>hurr closed glass cylinder is a closed system
>durr closed metal box is not a closed system
why did this thread attact so many pseuds?

>>11469000
I was right, you were wrong.
Get fucked pseuds.

>It weighs the same whether the fly is hovering in the
middle of the jar or landed on the floor of the jar. Basically, when you weigh the jar you are weighing the jar and all of its contents. Another example, if the jar has air in it, the jar will weigh more than a jar that has been evacuated and just contains a vacuum.

>Long answer is that it does depend slightly on whether the fly is moving (well, actually, whether the fly is accelerating). With the fly in the air the jar could weigh more or less than with the fly standing on the floor of the jar, depending on whether the fly begins moving up or down. Let's just say the average weight of the jar+air+fly when the fly is flying is the same as the weight with the fly on the floor of the jar."

>"Since the jar is closed when it is weighed all of its contents are being weighed. (jar, lid, air, and flies no matter the positin of the flies.) The flies in motion would still put pressure on the air then the jar then the scale."

>>11472320
The flies aren't jumping up and down on the ground. The same problem with a bowl of water and fish wouldn't have the weight change. Stay retarded.

>>11472335
correct. i was merely trying to show that weight isn't always mass*gravity as these high school dropouts think. Even so, the weight read by the scale is still not 1.5kg because some of the force is dissipated to air that eventually pushes against the surface of the planet itself instead of the scale

>>11472341
The jar is sealed

>>11472316
Force is a vector, independent components are conserved independently. The vertical component of force can't magically be offset by horizontal components.

>>11472320
The elevator box is not a closed system you fucking retard.

>>11472370
Yes but the downward thrust from the fly is not equal to mass*gravity because part of lift from forward motion

>>11472376
Horizontal acceleration is caused by horizontal thrust, which does not affect the downward weight. The horizontal and vertical components are independent.

>>11472379
Yes and said horizontal momentum creates an upward force when the air passes the fly.

Doesn't saying that it weighs <1.5Kg necessarily require the supposition that the flies are exerting force on air outside of the jar?

1.5kg. eventually the flies will die and fall to the ground. and exert force on the scale

>>11472381
It literally can't, go back to your fundamentals. Vertical lift on the fly must be entirely generated by changing the vertical component of momentum of the air, which affects the vertical component of momentum of the jar.

>>11469000
Ah, yes. One of the famous unsolved problems in physics.

Checked.

>>11469000
>Another flies in jar thread.

>>11472372
>>11472366
elevator is sealed just like the jar and you guys are both massive retards. there is no difference between the closed elevator and the closed jar.
>WAAHHH MY HIGH SCHOOL PHYSICS TEACHER ONLY GAVE US SIMPLE PROBLEMS WITH CLOSED SYSTEMS AND TOLD US THAT WEIGHT = MASS*GRAVITY, SO I MUST SOLVE ALL PROBLEMS THIS WAY EVEN IF THE ASSUMPTIONS ARE INAPPROPRIATE!! NOOO STOP POINTING OUT THAT I"M A RETARD!!!

>>11472389
think about billiard balls. two colliding billiard balls on vertical paths can end up on mostly horizontal trajectories.

>>11472412
How can the air exert forces on the rest of the earth's surface if the air can't escape the jar? Use your brain for a second.
>>11472418
The horizontal and vertical components of momentum of the billiard balls are conserved independently. In your case, the net horizontal and vertical components are both zero. The components will always both be zero, as long as the system is closed. There's no way for the net horizontal component to end up at 1 unit and the vertical at -1 unit, which is what you're implying.

>>11472427
air pushes on jar wall and in turn air outside the jar pushes back on the outside of the jar wall.

>>11472412
1. Elevator isn't hermetically sealed like the jar.
2. Elevator is suspended in the air by the elevator cable, when you jump up and down you are exerting increased pressure on the tensile strenght of the cable. These cables have a certain amount of flexibility.
3. Flying is not the same as jumping up and down.

>>11472387
Nobody has responded to my question. Does this mean that I'm right and anybody who says <1.5Kg is a retard?

>>11472439
And this is somehow supposed to allow momentum exchange between the inside and outside air? The jar is held fixed in place by friction with the scale, so the jar walls don't accelerate at all relative to the Earth.

>>11472446
Yes, you are right.

>>11471957
is this possible? could you maxwells demon the problem to make it have buoyancy?

here is whats happening at the local level of the flys wing
https://www.youtube.com/watch?v=ZCbZZ8OpP-g

>>11472444
holy shit you're dumb. we are assuming the elevator is just as sealed as the jar. scale being cables vs being a platform doesn't matter. just neck yourself, stop shitting up the board.

Dude its 1.5kg, here's how to answer it for brainlets. All right the the sum of the mass of air and flies within the jar is a consistent .5kg. Brainlets think that just because the flies are flying (who would've thought) that somehow there's magically less mass. Now imagine if the image had the same amount of flies but they were all dead and lying lifeless in the jar, boom, it would be the same as the flies flying in the enclosed space and such would be 1.5kg being exerted...

>>11471467
Fucking stupid

>>11472496
>arguing that because mass stays the same, weight stays the same
if the flies all died at the same time, the jar would only weight 1kg while they all fell to the floor, despite a constant mass of the system.

>>11472499
Good argument

>>11472471
>we are assuming
Who is this 'we'?
All I see is a single retard (You) that came up with a harebrained example that has nothing to do with the OP, and is grasping at straws to defend his bullshit from five different anons calling him out on it.

>the elevator is just as sealed as the jar
No it's not. The jar is a closed system and the elevator is not. The elevator is not hermetically sealed while the jar is.

>just neck yourself, stop shitting up the board.
Ironic, you fucking brainlet retard.

By the way, I have already posted the solution. Whether the flies are resting or flying around has no impact whatsoever on the weight of the jar.

https://how2physics.com/2017/02/12/jar-of-flies/
https://myemail.constantcontact.com/Jar-Of-Flies---Explained-.html?soid=1101802259576&aid=i8a90gU7jjM

Neck yourself. Or even better, go jump off an elevator shaft.

>>11472504
It only weighs 1 kg while the center of mass of the jar+flies is accelerating down. As long as the center of mass doesn't accelerate on average, the weight of the closed jar will average 1.5 kg.

>>11469274
this.

>>11469000
1kg becuase the flies are not exerting a downwards force onto the scale

when will mods start moving this thread to /s4s/ or /trash/?

>>11471463
Oh that's why when I jump above a scale it tells me my weight before I actually touch it. Damn.

>>11469296
>plane flied over head
> crushed to death.

>>11472843
The air doesn't exert a force to keep you from falling when you jump retard

>>11472306
>There's less normal force on you when gravity is actively accelerating you
Strange.

>>11472098
>what is gravity
lol

>>11469000
I'm crashing this thread, No survivors.
https://www.youtube.com/watch?v=N0IGrSjcBZs

>>11474581
/sci/ btfo

>>11469005
(you)

>>11469000
>The jar is clearly sealed, therefore it's weight is 1.5 kg.
Now, WHERE CAN I GET SOME TENTH OF A KILOGRAM FLIES!!!!!!!!

>>11474515
air is a fluid

>>11474581
What's the fucking point of using a lightweight drone and a scale so shitty that it always marks zero? Even when rhe drone was resting it was marking zero.

We want to see if the weight actually DROPS or not. Fuck you and your shitty video that answers nothing.

>>11469261
kek

>>11475216
>I don't know what tare is.
Why don't you just go back to whatever low IQ board you came from.