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Author Topic: Does a fly flying inside an aircraft add to its weight?  (Read 13250 times)

Shane Field

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Shane Field asked the Naked Scientists:
   
Does a fly flying inside an aircraft add to its weight?

What do you think?
« Last Edit: 14/11/2010 14:30:02 by _system »


 

Offline maffsolo

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Does a fly flying inside an aircraft add to its weight?
« Reply #1 on: 14/11/2010 14:50:00 »
Shane Field asked the Naked Scientists:
   
Does a fly flying inside an aircraft add to its weight?

What do you think?

I believe when, and only when, the fly lands on any part of the aircraft's surface during the duration.
 

Offline GlentoranMark

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Does a fly flying inside an aircraft add to its weight?
« Reply #2 on: 14/11/2010 16:43:55 »
The fly and all the air molecules would add to the overall weight of the plane but getting a pair of scales to travel at 400 mph would be a bit tricky.
 

Offline maffsolo

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Does a fly flying inside an aircraft add to its weight?
« Reply #3 on: 14/11/2010 20:43:57 »
Since the fly entered the plane, or your own restroom, the fly has displaced the air around it.
As long as the insect fly is airborn the air around it is in  turbulance, not placing a constant pressure against anything except its own wings, upper or lower part.

The plane can be in any state sitting still on a fine weight scale and as long as the insect fly is airborn, its mass will not register at that moment on the fine weight scale.
 

SteveFish

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Does a fly flying inside an aircraft add to its weight?
« Reply #4 on: 16/11/2010 02:36:25 »
Maffsolo:

In order to remain aloft a fly has to push air downward. The downward moving air will transfer its kinetic energy to the floor of the airplane cabin. The weight of the airplane, in our gravity field, and the mass of the airplane wherever it is, will be constant regardless of what the fly is doing.

Steve
 

Offline maffsolo

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Does a fly flying inside an aircraft add to its weight?
« Reply #5 on: 16/11/2010 02:46:05 »
Maffsolo:

In order to remain aloft a fly has to push air downward. The downward moving air will transfer its kinetic energy to the floor of the airplane cabin. The weight of the airplane, in our gravity field, and the mass of the airplane wherever it is, will be constant regardless of what the fly is doing.

Steve
I disagree
The turbulence of the fly's wing to wind pressure will dissipate long before it will reach the floor.
Let's say it is like blowing out a candle at 4 feet away.
It is difficult even if you can blow that hard, and I think there is more wind energy there than a fly can produce.
« Last Edit: 16/11/2010 02:48:03 by maffsolo »
 

SteveFish

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Does a fly flying inside an aircraft add to its weight?
« Reply #6 on: 16/11/2010 03:15:17 »
Maffsolo, the momentum of the moving air transfers to the airplane, otherwise where does it go?
 

Offline maffsolo

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Does a fly flying inside an aircraft add to its weight?
« Reply #7 on: 16/11/2010 04:19:44 »
When you blow across the room to die out a candle where does that go?
 

Offline Geezer

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Does a fly flying inside an aircraft add to its weight?
« Reply #8 on: 16/11/2010 05:08:09 »
It makes no difference whether the fly is sitting in First Class, or flying around the bog in Tourist. The air in the plane is part of the plane, and that air is supporting the weight of the fly.

If the fly was in the air in the cabin while the plane climbed from sea level to 35,000 feet, did the fly increase its elevation by 35,000 feet without any help from the aircraft? I don't think so :D
 

Offline Bored chemist

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Does a fly flying inside an aircraft add to its weight?
« Reply #9 on: 16/11/2010 19:48:58 »
When you blow across the room to die out a candle where does that go?
The momentum you impart to the air spreads out as it leaves your mouth at a large distance it is spread across a large area. At a great enough distance the momentum is no longer great enough to put the flame out because the flame only intercepts a small part of the moving air.
 

Offline maffsolo

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Does a fly flying inside an aircraft add to its weight?
« Reply #10 on: 16/11/2010 21:41:12 »
It makes no difference whether the fly is sitting in First Class, or flying around the bog in Tourist. The air in the plane is part of the plane, and that air is supporting the weight of the fly.

If the fly was in the air in the cabin while the plane climbed from sea level to 35,000 feet, did the fly increase its elevation by 35,000 feet without any help from the aircraft? I don't think so :D
35000 feet...
If the fly is the observer would that be relative to its environment?
 Fly sees the inside hull of the plane as if it were standing still.
 The fly will not know the difference until, it sticks its head out the window.

Flies are never in first class anyway, they can not afford the luxury...
 
Hey Geezer that is slick thinking, of course the air supports the fly's weight, but does that portion of air supporting the fly's weight depend on transferring the fly's  weight to the hull of the plane, to support the fly in its own flight, besides life support?

Maybe it all the passengers went to first class and pushed on the cabin door the plane will go faster.  ;D

When you blow across the room to die out a candle where does that go?
The momentum you impart to the air spreads out as it leaves your mouth at a large distance it is spread across a large area. At a great enough distance the momentum is no longer great enough to put the flame out because the flame only intercepts a small part of the moving air.


Exactly that is what I was getting at...thanks Bored Chemist

A breath of air being exhaled, produces more wind current energy, than the air from the turbulence from a fly as it is in flight.
« Last Edit: 16/11/2010 21:49:37 by maffsolo »
 

Offline Bored chemist

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Does a fly flying inside an aircraft add to its weight?
« Reply #11 on: 17/11/2010 06:58:25 »
Momentum is a conserved property.
If you blow across the room you can make the curtains move because they are big and intercept a  lot of the air you moved by blowing.

It's really very simple- the fly is held up by the air. The air is held up by the plane and if the plane were held up by a set of scales then they would show the fly's weight as well as the plane's.
What else could be holding up the fly?
 

Offline maffsolo

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Does a fly flying inside an aircraft add to its weight?
« Reply #12 on: 17/11/2010 10:06:23 »
Momentum is a conserved property.
If you blow across the room you can make the curtains move because they are big and intercept a  lot of the air you moved by blowing.

It's really very simple- the fly is held up by the air. The air is held up by the plane and if the plane were held up by a set of scales then they would show the fly's weight as well as the plane's.
What else could be holding up the fly?


Ok let'say the plane's cabin is balanced on a beam lever, initially with the fly in flight at one end of the cabin if the fly flew to the other end will the cabin tilt?

When a training cabin for astronauts begins the parabolic dive is it the air that supports the trainees' bodys as free fall begins?

Since the molecules of the fly and the molecules of air surrounding the fly are in support, the plane's ballistic acceleration  affects the fly and the air in the plane, will the air be more dense at the rear of the plane?

This is what is confusing me... even though the fly's support makes a point.

OK I surrender I am wrong and pass the appology to all in this thread

« Last Edit: 17/11/2010 11:29:47 by maffsolo »
 

Offline CZARCAR

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Does a fly flying inside an aircraft add to its weight?
« Reply #13 on: 18/11/2010 02:21:27 »
Momentum is a conserved property.
If you blow across the room you can make the curtains move because they are big and intercept a  lot of the air you moved by blowing.

It's really very simple- the fly is held up by the air. The air is held up by the plane and if the plane were held up by a set of scales then they would show the fly's weight as well as the plane's.
What else could be holding up the fly?

vvv!
 

Offline peppercorn

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Does a fly flying inside an aircraft add to its weight?
« Reply #14 on: 22/11/2010 10:40:01 »
That means that if I lift the plane and put a scale under it, the scale should measure the weight of the plane eventhough the plane is not actually on the scale and not touching it but rather above it, is that true?

Of course not. If the plane is not resting on the scale (it's suspended from a cable, say) no force is transferred downwards to the scale.
It's the fact that, with the plane idea, the fly is flying in a closed box (effectively) that makes its weight additional to the weight of the box (or plane).
 

Offline CZARCAR

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Does a fly flying inside an aircraft add to its weight?
« Reply #15 on: 22/11/2010 13:04:18 »
the plane is on the scale & the fly drops from flight & hits the floor, wouldnt this force increase the weight of the plane temporarily? then the fly takes off upwards, wouldnt the air pressure/force from the ascending fly also increase the weight of the plane temporarily?
 

Offline peppercorn

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Does a fly flying inside an aircraft add to its weight?
« Reply #16 on: 22/11/2010 14:52:21 »
the plane is on the scale & the fly drops from flight & hits the floor, wouldnt this force increase the weight of the plane temporarily? then the fly takes off upwards, wouldnt the air pressure/force from the ascending fly also increase the weight of the plane temporarily?

The scales will experience a tiny amount more force and record the change as such, but this is because a set of scales can't distinguish between force from gravity and any other mechanical force acting upon it.

This getting 'off topic' from the OP though.
 

Offline CZARCAR

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Does a fly flying inside an aircraft add to its weight?
« Reply #17 on: 22/11/2010 17:00:12 »
the plane is on the scale & the fly drops from flight & hits the floor, wouldnt this force increase the weight of the plane temporarily? then the fly takes off upwards, wouldnt the air pressure/force from the ascending fly also increase the weight of the plane temporarily?

The scales will experience a tiny amount more force and record the change as such, but this is because a set of scales can't distinguish between force from gravity and any other mechanical force acting upon it.

This getting 'off topic' from the OP though.
the fly keeps flying up & dropping down & i think that will affect the fuel mileage of the plane?actually i think the fly burns its fat as fuel for the ascension so  does the expended fat relasing its force in this manner result in lower mpg because the fat has been converted to energy?& the answer is YES , the downward propulsion of air due to the flying fly results in flyfat converted into energy released? WHAT IF THE FLY WAS FLYING AGAINST THE CEILING, TRYING TO RAISE THE PLANE?
« Last Edit: 22/11/2010 17:34:14 by CZARCAR »
 

Offline peppercorn

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Does a fly flying inside an aircraft add to its weight?
« Reply #18 on: 22/11/2010 19:09:21 »
WHAT IF THE FLY WAS FLYING AGAINST THE CEILING, TRYING TO RAISE THE PLANE?
But its wings are only acting against the air inside the plane, so it still has no outside effect. ie. Its a still closed system.
 

Offline CZARCAR

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Does a fly flying inside an aircraft add to its weight?
« Reply #19 on: 22/11/2010 19:56:42 »
system is closed except for gravity. as the fly flies, its exerting downward pressure from wings- if it pushes up it might negate the down pressure but i doubt it..........fact is, fly is burning its fat/fuel to fly as it remains afloat
 

Offline Joe L. Ogan

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Does a fly flying inside an aircraft add to its weight?
« Reply #20 on: 22/11/2010 20:10:45 »
Momentum is a conserved property.
If you blow across the room you can make the curtains move because they are big and intercept a  lot of the air you moved by blowing.

It's really very simple- the fly is held up by the air. The air is held up by the plane and if the plane were held up by a set of scales then they would show the fly's weight as well as the plane's.
What else could be holding

The airpressure on the oustside of the plane nullifies the weight of the air inside the airplane unless the inside is pressurized!  Thanks for comments.  Joe L. Ogan
 

Offline CZARCAR

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Does a fly flying inside an aircraft add to its weight?
« Reply #21 on: 22/11/2010 20:26:57 »
i can stand on a truckbed. when i jump up, the bed goes down. when i land the bed goes down.= dead fly aint gonna make a diff, live fly will burn fat to fly& unless its pushing on the ceiling of the plane?
 

Offline peppercorn

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Does a fly flying inside an aircraft add to its weight?
« Reply #22 on: 22/11/2010 22:52:14 »
Ok, say I have a really large (sealed) room, and I repeat the experiment in it, what would happen?

Well, as a closed system (assuming thermally closed as well) I guess the only place for any of the chemical energy stored in the fly (as it flies, hits floors, etc) is into heat - warming the air temp infinitesimally.
 

Offline CZARCAR

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Does a fly flying inside an aircraft add to its weight?
« Reply #23 on: 23/11/2010 11:02:30 »
The fly in order to fly has to burn its flyfat. The fly flies up into the ceiling of the plane with as much force as it delivers to the floor of the plane as it drops after hitting the ceiling. The fly gets lighter as it converts flyfat to energy...the fly is flying against the force of gravity?
« Last Edit: 23/11/2010 11:07:08 by CZARCAR »
 

Offline elfabyanos

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Does a fly flying inside an aircraft add to its weight?
« Reply #24 on: 25/11/2010 11:12:30 »
The fly does add to the weight of the system. Plane + air + fly + anything else that is inside the plane = weight of plane system.

The only way the fly can change the weight of the plane is by either altering the mass of itself, the air or the plane, or by altering the strength of gravity. The fly cannot do this, therefore it cannot affect the weight.

All the situations proposed do not affect the weight. They affect forces.

If the fly flies up and hits the ceiling the plane will experience a momentary upwards force as the fly transfers the energy of its momentum to the plane. The fly generated that momentum by turning chemical energy into kinetic energy. An equal amount of energy was expended pushing air downwards as was expended pushing the fly upwards. The kinetic energy of the air going downwards is dissipated to a certain extent over time. It will take longer, but a much larger mass of air will hit the bottom of the plane at a much lower speed than the fly which hit the ceiling fast. Nonetheless the result of a small fly going fast and a large amount of air going slowly but in the opposite direction will eventually cancel. That the air and the fly do not transfer the forces at the same time is irrelevent, except that it would cause the temporary wobbles up and down.

The plane will bob up and down slightly over this period, but this will not affect the result. Same as if you stand on a boat and rock it side to side.

Ultimately you or the fly can temporarily upset the system in a number of ways, as can any other element within that system. But that is not a question of weight, which exerts a constant force due to gravity at all times, without variation. It is all the other forces which are invoked by the thought experiment of the fly flying around the plane.
 

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Does a fly flying inside an aircraft add to its weight?
« Reply #24 on: 25/11/2010 11:12:30 »

 

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