how much air does an A380 shift?
Discussion
Simpo Two said:
BarnatosGhost said:
If I remember correctly I think he'd been challenged to work out whether the king's crown had been made of pure gold, or of a gold alloy. Displacement gave him the ability to work it out, since a pure gold crown would displace the same amount as a lump of gold of the same weight as the crown. An alloy crown would be displace a different amount to that same lump of gold.
That's like asking 'Which is heavier, a pound of lead or a pound of feathers?'Assuming both crowns were heavier than water, if they were the same volume they'd displace the same amount of water. 1cm3 of metal displaces 1cm3 of water; it has no option whatever it is (unless it floats). But combining volume with weight gives density, which is probably what you were thinking of
Then the crucial final question is whether the crown displaces the same amount of water as the lump of gold. If it didn't, then it wasn't pure gold.
R300will said:
Zad said:
Cross-section area * velocity (in metres/second) * density of air at that altitude.
Air density @ sea level = 1.225 kg.m^3
Relative density @ 10,000M = 0.333
Mach 0.84 = 283m/s
Cross sectional area .. dunno, 150m^2?
That is approximately 17,000kg or 17 tonnes of air directly displaced.
As to indirect displacement, how much air the engines the move, or the drag induced on the system, that's a whole different kettle of fish and can of worms.
Beat me too it but i agree with the maths shown above.Air density @ sea level = 1.225 kg.m^3
Relative density @ 10,000M = 0.333
Mach 0.84 = 283m/s
Cross sectional area .. dunno, 150m^2?
That is approximately 17,000kg or 17 tonnes of air directly displaced.
As to indirect displacement, how much air the engines the move, or the drag induced on the system, that's a whole different kettle of fish and can of worms.
Blackpuddin said:
R300will said:
Zad said:
Cross-section area * velocity (in metres/second) * density of air at that altitude.
Air density @ sea level = 1.225 kg.m^3
Relative density @ 10,000M = 0.333
Mach 0.84 = 283m/s
Cross sectional area .. dunno, 150m^2?
That is approximately 17,000kg or 17 tonnes of air directly displaced.
As to indirect displacement, how much air the engines the move, or the drag induced on the system, that's a whole different kettle of fish and can of worms.
Beat me too it but i agree with the maths shown above.Air density @ sea level = 1.225 kg.m^3
Relative density @ 10,000M = 0.333
Mach 0.84 = 283m/s
Cross sectional area .. dunno, 150m^2?
That is approximately 17,000kg or 17 tonnes of air directly displaced.
As to indirect displacement, how much air the engines the move, or the drag induced on the system, that's a whole different kettle of fish and can of worms.
What about the several tons of air sucked, squeezed, banged and blown out the back? Wouldn't that change the whole equation?
R300will said:
apparently so according to the story. i mean if you shape it right yes but that is displacement. if you are relying on pure density then i doubt any metal will foat, even mercury.
Several metals float - you almost certainly saw some of them float at school; sodium, potassium, lithium. Not sure why you would think of mercury, it's pretty bloody dense stuff!
Chuck328 said:
Blackpuddin said:
R300will said:
Zad said:
Cross-section area * velocity (in metres/second) * density of air at that altitude.
Air density @ sea level = 1.225 kg.m^3
Relative density @ 10,000M = 0.333
Mach 0.84 = 283m/s
Cross sectional area .. dunno, 150m^2?
That is approximately 17,000kg or 17 tonnes of air directly displaced.
As to indirect displacement, how much air the engines the move, or the drag induced on the system, that's a whole different kettle of fish and can of worms.
Beat me too it but i agree with the maths shown above.Air density @ sea level = 1.225 kg.m^3
Relative density @ 10,000M = 0.333
Mach 0.84 = 283m/s
Cross sectional area .. dunno, 150m^2?
That is approximately 17,000kg or 17 tonnes of air directly displaced.
As to indirect displacement, how much air the engines the move, or the drag induced on the system, that's a whole different kettle of fish and can of worms.
What about the several tons of air sucked, squeezed, banged and blown out the back? Wouldn't that change the whole equation?
The original question was air "shoved aside".
otolith said:
R300will said:
apparently so according to the story. i mean if you shape it right yes but that is displacement. if you are relying on pure density then i doubt any metal will foat, even mercury.
Several metals float - you almost certainly saw some of them float at school; sodium, potassium, lithium. Not sure why you would think of mercury, it's pretty bloody dense stuff!
R300will said:
otolith said:
R300will said:
apparently so according to the story. i mean if you shape it right yes but that is displacement. if you are relying on pure density then i doubt any metal will foat, even mercury.
Several metals float - you almost certainly saw some of them float at school; sodium, potassium, lithium. Not sure why you would think of mercury, it's pretty bloody dense stuff!
R300will said:
They are alkaline metals, not the transition metals i had in mind. The transition metals hold more of a metallic definition in my eyes but its a good shout although they don't really float for long as they dissolve/explode quickly. The samples i have seen stored in oil seem to be at the bottom of the flask though
Sure, but they're still metals. And they would still float if you gave them a thin coat of something waterproof.They sink in oil because oil is less dense than they are (and less dense than water - we know that, oil also floats!)
Sodium is ~ .97g/cubic cm, the paraffin it is stored in is ~0.8g/cubic cm and water is (obviously) ~1.0g/cubic cm.
otolith said:
R300will said:
They are alkaline metals, not the transition metals i had in mind. The transition metals hold more of a metallic definition in my eyes but its a good shout although they don't really float for long as they dissolve/explode quickly. The samples i have seen stored in oil seem to be at the bottom of the flask though
Sure, but they're still metals. And they would still float if you gave them a thin coat of something waterproof.They sink in oil because oil is less dense than they are (and less dense than water - we know that, oil also floats!)
Sodium is ~ .97g/cubic cm, the paraffin it is stored in is ~0.8g/cubic cm and water is (obviously) ~1.0g/cubic cm.
17 tonnes for an A380? I assume thats 17 tonnes/second which seems remarkably low.
http://www.allstar.fiu.edu/aero/Flightrevisited.pd...
"Let us do a back-of-the-envelope calculation to see how much air a wing might divert. Take for
example a Cessna 172 that weighs about 2300 lb (1045 kg). Traveling at a speed of 140 mph (220
km/h), and assuming an effective angle of attack of 5 degrees, we get a vertical velocity for the air
of about 11.5 mph (18 km/h) right at the wing. If we assume that the average vertical velocity of
the air diverted is half that value we calculate from Newton's second law that the amount of air
diverted is on the order of 5 ton/s. Thus, a Cessna 172 at cruise is diverting about five times its
own weight in air per second to produce lift. Think how much air is diverted by a 250-ton Boeing
777."
http://www.allstar.fiu.edu/aero/Flightrevisited.pd...
"Let us do a back-of-the-envelope calculation to see how much air a wing might divert. Take for
example a Cessna 172 that weighs about 2300 lb (1045 kg). Traveling at a speed of 140 mph (220
km/h), and assuming an effective angle of attack of 5 degrees, we get a vertical velocity for the air
of about 11.5 mph (18 km/h) right at the wing. If we assume that the average vertical velocity of
the air diverted is half that value we calculate from Newton's second law that the amount of air
diverted is on the order of 5 ton/s. Thus, a Cessna 172 at cruise is diverting about five times its
own weight in air per second to produce lift. Think how much air is diverted by a 250-ton Boeing
777."
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