>be professor >final exam time >give my 6 years old

Its 1kg

>>8812919
no its 1.5kg

>>8812922
No its 0.5kg

>>8812919
>>8812922
>>8812923
Wrong it is 7kg

>>8812924
>>8812923
>>8812919
>>8812922
Wrong, it is 31.4 kg

1.5 kg
The flies have to push air down to stay in the air. The scale sees the 1kg from the jar itself and the 0.5 kg from the pushed down air.

>>8812936
What if all flies are momentarily falling ?

>>8812936
and would that be right with a plane for example ?

>>8812940
nice

>>8812913
College professors teach more to their six year olds than to their students. And taxpayers still pay for your wages. Sad!

>>8812940
Then their falling bodies are pushing down the air.

>>8812936
>>8812941
>3am sleeping
>hear a rumbling
>getting louder
>look outside, see airplane cruising at an altitude of 35,000 feet
>gonna fly right over my house
>FUCK
>run outside and watch my house be crushed by the downward pushed air.
>plane keeps flying, leaving a destructive trail of downward pushed air in it's path
But yea bro it's 1.5 kg moron

>>8812952
this is a really poor statement

>>8812940
>>8812952
No, the scale would show 1kg in that case until they hit the ground.

As long as the center of mass of the jar+flies system stays constant then the scale shows 1.5kg.

>>8812959
finally someone, who understands basic physics

You and your son are fucking retards.

>>8812919
>>8812922
>>8812923
>>8812924
>>8812925
wrong, any value it might have is meaningless

>>8812957
the force generated by the plane is really well distributed in the atmosphere, so what you are implying is sheer retardness

>>8812964
it acutally is a really nice problem

>>8812969
the task was to find what the scale read, so your existence is meaningless

>>8812969
>t. nihilist

>>8812964
kek typical brainlet, "i can't solve dis s1mple ez ekwuazion is da prohfesirs fawlt!!1!11one"

>>8812959
But then what constitutes the "jars+flies system"?

If you removed the lid would the scale drop by both the lid amount and the flies, or just the lid (so long as the flies remained within the jar)?

>>8812959
you are actually retarded

>>8812984

I'm not a physicist, but that's how I understand it :
Since the fly stay in the air, they are somehow transfering their weight to the air that supports them. That weight is then applied on the scale via air pressure.

If you open the lid, then the weight will stay the same, except if the fly leave and their weight gets distributed on a larger area.


>>8812988
nice trolling m8;
I took your bait.

>>8813002
No, it needs speed relative to the air that supports it, not the ground.

>>8812957
kekd

>>8812913
The answer is the sum of the first 2 milion primes

>>8812919
Of course it is!

The real question is, how do you get half a kg of flies into such a small jar?

Depends, are the flies sleeping?

How much does the air weigh

The answer is how the fuck are you fitting .5 KG of flies into a 1 KG jar... the flies would likely be so jammed together that they couldn't move and thus would weigh the .5 KG

Also what does a compacted group of flies look like?

>metric system

How the fuck am I supposed to do math in those fucked up units?

>>8813020
>fucked up units

found the murifat. The metric system is great

File: image.jpg (143KB, 852x655px) Image search: [Google]

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your image is misleading OP

Mythbusters did this shit in like 2009.

https://youtu.be/lVeP6oqH-Qo

Jump to 2:18 for them doing it with an RC helicopter for better data.

Weight of the jar will not change unless the lid is removed. If the lid is removed, the weight of the jar will drop by the weight of the lid, plus a percentage of the weight of the flies determined by the amount of air displaced by their wings that is pushing outward or upward and out of the jar instead of downward.

>>8812959
>>8812960
Agree with 1kg. But is that really the correct explanaition?
Suppose the flies behave like helicopters, so center of mass stays constant but the scale would show 1kg. Isn't the explanation that the lift force compensates gravitational force? It's basically about the difference between weight (1kg) and mass (1.5kg), isn't it?

>>8813046
Oy! I'm Murican, and am fine with metric.
>>8813020
is just a contributor to the 7%.

>>8812922
This is the only correct answer. However, it is the average of the weight. Every time they flap their wings the pressure makes it weight more for a brief moment then less for a brief moment. The average of that will be 1.5kg. Most scales won't be able to show that weight change since it is so insignificant. There's also the problem of more than one creature flapping its wings. The original experiment used a single bird to get these types of results.

>this thread again
>all these complete fucktards

>>8813425
Do you think a scale displays milliseconds you fucking moron???? Go back to kindygarten retard

In theory there should be 1.5, in reality the downwards air produced by the birds wings won't flow perfectly the floor surface, there will be turbulence and fluid friction along the way meaning it will weigh very slightly less than 1.5, and the difference in weight is made up by increased temperatures

File: cry_kek.png (572KB, 600x580px) Image search: [Google]

572KB, 600x580px

>>8812936
>be me
>come to /sci/ for the first time after a long absence
>"5 flies can generate half a kilogram of downward thrust"
nevar change

>>8812919
>>8812922
>>8812923

Who says we're not the smartest board on 4chan?

>>8813008
31.381.137.530.481 ?

>>8813073
>He thinks weight and mass both have units of kg

SI masterrace amirite senpai?

>>8813654
They can if there's enough of them to weigh 0.5kg, which the pic has established.

>>8812913
>>8812936
Yes this is correct if the jar is sealed. And ideal conditions are assumed.

>>8813654
It takes exactly as much force to fly as the weight of the flies. If they were supplying less force than their weight they won't go up at all. The weight that is lost is gained back by the force they send downwards to fly.

This is all assuming ideal conditions. In particular that the force supplied by the flies goes straight down with none going off to the sides. Also if the jar isn't sealed the air that mediates the force can go upwards due to pressure differences. So in realistic circumstances, regardless of whether the jar is sealed, the weight measured by the scale would be a little less than 1.5 kg.

Bernoulli's principle says that if the lid is on the jar then the air pressure will stay in the jar, so the flies being in the air doesn't matter and the jar would weigh 1.5kg.
If the lid isn't on the jar then the air pressure can escape and the jar would only weigh 1kg if the flies were flying.

Somewhere in between 1kg and 1.5, it would fluctuate. The push of the flies wings down is going to be negligible, the air they are pushing on doesn't travel straight down, it undergoes turbulence, and pushes on the walls, floor and lid of the jar. The force of their wingbeats gets diluted by the time it hits any given wall of the jar, and it would be negligible. However, any time one of the flies landed, it would put the weight closer to 1.5kg.

>>8814089
What if the lid has breathing holes? If it's an air-tight lid, wouldn't the flies die? poor flies

>>8814098
Then it'd weigh somewhere between 1kg and 1.5kg, cause only some of the pressure would be released

>>8812952
they're not in equilibrium though DUHHH

>>8813654
the jar might just be really tall and they're speeding upwards

>>8813654
welcome back, friendo

Time average is 1.5 kg
A discreet reading will be some value greater than 1.0 Kg

File: bird wing.webm (3MB, 1388x1048px) Image search: [Google]

3MB, 1388x1048px

>>8813436
Stop being an idiot. No one implied that. You where just being taught something you didn't know.

http://www.bbc.com/news/science-environment-30797983

>>8813060
TROLLS BTFO

Hnestly though, why isn't this video the first thing posted?

>>8815314
This is like the 102nd thread for this copy pasta. The turn around rate for /sci/ is too high. There are too many newfags. The real question is that why are you the only person to reply to that post?

>>8812998
>physics problem
>"im not a physicyst BUTTTT"
Just stop kid

>>8812913
Is the jar sealed?

>>8815327
DON'T CALL ME "KID", SON.

>>8815277
Really cool, never seen this vid. Thanks

>>8814020
It's exactly the opposite, if the jar is sealed no additional weight will be measured because the system is closed and any force will only be exerted on the boundaries of the jar. If not sealed we will measure 1.5kg.
If thats too abstract for you, imagine the whole thing upside down with the opening on the ground an the flies exerting a force of say 2kg trying to lift the jar, if the flies weight are less than 1kg they would lift it. Now you seal the jar and by your logic it should start to levitate with no air flow whatsoever, that would be really stupid to assume wouldn't it?

>>8812913
Your wife's son is an asshole.

>>8816273
Kek

>>8812936
Wrong, flies generate antigravity to stay afloat so it's 0.5kg.

>>8812913
Did you do the experiment?

What if we have a sealed jar that weighs 0kg, and all the flies try to fly upwards through the lid?

>>8815851
>It should start to levitate
There is no net force in given system

>>8812957

This is retarded.

Their wings would have to be completely in sync to be 1.5 kg and even then it'd fluctuate on the down and up stroke of each wing beat.

>professor
>shitposts of 4chan while Farming his exams out to 6 year olds
>mocks his students for not knowing more about physics
>neck yourself. You're the problem dumbass.

Replace the air and flies with water and fish.

1kg

>>8816678
>t. 93% here

>>8817054
Why is everyone else so retarded anon? I feel alone :(

>>8812947
Go away trump

>>8813005
If we had a long enough treadmill, would it accelerate?

>>8817057
I'm afraid you feel alone because you and him are actually the retards that do not understand Newton's third law:

http://rsif.royalsocietypublishing.org/content/12/104/20141283

Just wait for them to land and it will for sure weigh 1.5.

The flies weigh half as much as the jar?!

Did these flies come from /fit/ or something?

>>8813005
>Implying an aeroplane takes off using powered wheels

>>8812913
it's 0 kg if you're in space

>>8812913
flies raise the density of the air in the same way replacing the air with another gas would, so i'ts 1.5 kg

But what if the jar is a car and the fly flies through a window in the car?

File: what.jpg (15KB, 290x297px) Image search: [Google]

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>>8812913

When you hold your hand out five feet in the air and slowly move it down, the air pressure directly under your hand may increase, but surely the air pressure at the ground level is unaffected and remains the same as it's surroundings.

I posit that the flies will indeed affect the distribution of pressure in the air but the net result on the bottom surface of the jar will be negligible.

In order to be more certain of this, the dimensions of the jar would need to be a known quantity.

>>8817993
>open system vs closed system
I posit that you are retarded.

>>8812913
The answer depends on how the scale is calibrated.

>>8818021
>not having a current NIST-traceable calibration
pleb NEET detected

>>8818028
Who calibrates the calibrators?

>>8818043
That question makes no sense, and I therefore will not respond to it.

>>8812936

<1.5kg

Flies have mass thereby making the jar denser than if it was empty, the buoyancy from the air is therefore greater.

File: help.jpg (7KB, 226x223px) Image search: [Google]

7KB, 226x223px

im blowing on my scales but nothings happening helppp

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>>8813019
>Also what does a compacted group of flies look like?
like this probably

googled "dead flies"

>>8816689
Your*

>>8812919
its 9.81kg/s^2

>>8812913
It's non intuitive that the flies in flight contribute to the weight. I don't have a problem with people not getting the problem right.

If you didn't teach the principle before giving out the question you're a total asshole.

>>8818216

See >>8818004

>>8815277
Wait, hold the fuck on. Shouldn't the integration of the green line give the same value as the black line? Why isn't there less weight when the bird is in freefall?

>>8819415
becuase muh gravity

>>8819415
seems like the green line is just aerodynamic force and not net force

>>8812957
>things that didn't happen

>>8812913
>flies weighs
teach your son some grammar OP

>>8812913
How many of the flies are on the side of the jar and how many are flying?

>>8812957
This is why planes always fly over roads

>>8812913
Between 1 and 1.5 kg. Have to take in the average, if we treat the flies as a high temperature .5 kg gas then there is an average kinetic energy that puts a force on the scale that is greater than 1 kg and less than 1.5 kg.

3 possible answers. 2 variables. 1 correct answer. Flies look like they are in a closed jar. 1kg because that is 2/3 of the highest possible outcome.

>>8812913
Well, reading the scale, 111111.

>>8813425
is it fair to assume they are flying. why not just falling? i don't see any evidence for either case. I'd say there is not a correct answer that can be reach with the data given

>>8812913
1 kg, the air displaced by the flies does not exert force directly downwards.

Those are some big ass flies

>>8821086
4u

>>8812957
This is why airplanes arent allowed to fly near the whitehouse

>>8812936

WRONG.

pushed down air molecules collide with other molecules, and very little of the downward force vector makes it to the bottom of the jar.

Most of it is spent pushing air molecules horizontally.

So it weighs ~1kg, in reality a tiny bit more.

>>8821103

also because they might voluntarily reaccomodate the president

oh wait, he does that for them, nvm

>mfw no one has a jar and some flies to test this

>>8821140
Actio = Reactio

For each force that pushes an air molecule to the left there's an equal force that pushes another air molecule to the right.

>>8812913
Jar + Flies + Air = a bit more than 1.5

>>8821140
Wrong yourself.
You're not considering the volume 500 g of flies take up - the majority aren't actually able to fly, it's too crowded.

>>8821144
kek
re-accommodate
new memey for 2k17

>>8812957
This is why every plane is accompanied by a mirror plane that flies upside down underneath the first.

>>8812913
That's a lot of flies in such a small jar. I suppose they are not even able to fly all at the same time. So the scale reads around 1,5 kg.

>>8812913
>weight
>kilogram

Because of buoyancy, the scale will actually read slightly less than 1.5 kg. And assuming the flies take up volume, it could change the results more.

>>8822459
Oh woops, I assumed the flies were dead. Never mind.

This is an old meme and from what I remember its a termodynamics problem not a mechanics one. I'm not sure the weights are simply additive, yet if we consider the flies as a "gas" and the scale to be a piston then the force provided by the flies is indeed additive to the initial weight.

>>8812913
How can we see the jar of flies if our eyes are not real?

>>8812978
"t."?