What make airplanes fly and stay in the air?
397146
A combination of two factors. Very basic answer here:\n\n\nNewtons' third law: for every action thee is an equal and opposite reaction. (air hitting the bottom of a wing forces the wing upward)\n\nBernoulli’s Principal: As the velocity of air increases, its pressure decreases. Wings are shaped as that the air travels faster over the wing creating a low pressure area. This area of low pressure over the wing 'sucks' the wing upward.
193979
Airplane wings use a combination of Bernoulli's principle (the faster air flows over a surface the lower its pressure) and "Reaction" or Newtonian lift, the force produced by the downward acceleration of an air mass by a plane surface that is tilted with respect to the velocity. (See 1st & 2nd references). The upper surface of the wing is curved and the lower surface is relatively straight. Thus air passing over the wing has farther to travel before it rejoins the air that went under the wing, and must move faster. The lower pressure over the wing creates a Bernoulli lift force. The wing also has a positive "angle of attack" (basically the tilt angle of the wing's lower surface) producing Newtonian lift. Ref. 1 estimates that airliners have more Newtonian than Bernoullian lift. The wing transfers the sum of these lift forces to the airplane. And of course the thrust needed to reach the speed necessary for the wings to provide adequate lift comes from a motor-driven propellor or a jet engine. \nBirds, having movable wings, fly in two basic modes, gliding and flapping. These modes also use a mix of Bernoulli's principle and Newtonian momentum exchange to achieve lift. When gliding, the curved wing surface operates similarly to that of an airplane. More momentum exchange occurs when the wings are flapped; each downstroke pushes air downward and backward which provides an upward and forward force to the wing and through the wing to the bird's body. Feathers play a vital and mechanically complex role in flight, especially in flapping. The 3rd reference discusses this in some detail. I can't put pictures in this answer but the 4th reference provides a diagram of gliding lift, and you can find much more by googling "aerodynamic lift birds".
32
A helicopter gets its power from rotors or blades. When its rotors are spinning, a helicopter doesn't look much like an airplane. But the rotor blades have an airfoil shape like the wings of an airplane. So as the rotors turn, air flows more quickly over the tops of the blades than it does below. This creates enough lift for flight.
254063
The same reason airplanes do. Its a matter of lift and drag, based on the shape of the wing. A frisbee is just a circular wing.
144449
you could flap your arms all day long a (BMPH) Billion Miles Per hour.heheh And you never get lift. See to under stand how birds fly you have to understand a birds body. First off a birds bones are hollow. Meaning less weight. Secondly the birds wings are shaped like a windfoil which gives lift. to explan how a wing works we will go into alittle physics of flight. To understand flight you have to understand how the wing is designed. \n\nfirst take a peice of postit note from one of the 5x3 inch pads. you need a pensile. bring the bottom side of the post it note to the top side where it is sticky. stick it together. Now you have a piece of paper simular to a tear drop. what you going to do is run the pencle between the opening to the other side. let the pice of paper float freely. hold the pencile with both hands one on one side of the paper and the other on the other side of the paper. Not put the not about 5 inches in front of your mouth and blow. Notice what happens the paper lifts. This is what is called lift. This is how birds fly. basicly when you blow on the paper the under side high presure goes under and low presure goes over the top. We will call it a win for now. But pending on how the wind is hitting it will depend on what direction the wing will go. If the tail end is faced up then the wing will go down it it's faced down the wing will go up. When it goes up that is called lift. and thats how birds fly.
801793
and gravity does what?\n\nand why don't you fall off?
1044571
Well, A plane's speed is way too low to leave Earth's atmosphere.  For something to orbit around the Earth, it would have to move at speeds of at least 40000 km/h or MACH 40, the fastest airplanes have only went at MACH 4.  Now a plane can fly because it uses the atmosphere to lift it up.  But once it gets higher and higher, the atmosphere becomes too light to lift the plane up so there will be a certain altitude when the altitude levels off and the plane will no longer climb.
1165909
All thing that flies except aeoroplane.
908073
Ummmm... Are you talking about sprint cars? They have aluminum "wings" on top. They contribute to the aerodynamics of the car. They also allow for additional handling adjustments. The position of the wing determines air flow which can either loosen or tighten the handling of a car. :) If you want to see a picture check out http://www.billthomasracing.com/ or http://www.rtschassis.com/.
241884
There are maritime stabilizers that “stabilize” a ship to dampen it’s natural tossing on rough seas.\n\nThere are aviation stabilizers, such as the horizontal stabilizer that is part of the tail empenage that controls the vertical axis of the airplane in conventional flight.\n\nThere are chemical stabilizers that “stabilize” a substance, preventing it from changing composition, such as the commonly used “STABIL” that is placed in gasoline fuel tanks to prevent the fuel from decomposing.\n\nJohnny
1162285
Aircrafts' wings gives the aircraft lift (i.e. shaped so that when wind passes through, it will be pushed up), and once a certain velocity is reached, the upwards lift is enough to counteract the forces of gravity (and exceed it), and thus they fly.\n\nSpaceships achieves escape velocity to escape from the Earth's gravitation (or at least far enough for the space ship to reach orbit). Then, at the orbit, it orbits earth at a certain velocity which gives it enough velocity to counteract the remaining attraction from Earth's gravity, hence it stays in space.
475251
If I remember correctly from my high-school physics class, it's a combination of gravity and one of Newton's laws of motion - the one that says "an object in motion stays in motion unless acted on by an outside force." So that force keeps it moving around and gravity keeps it from just flying off into space.
1137769
plane starts gliding...trading potential energy of its height to kinetic energy forward to hopefully find a landing site.  this is why airplanes gain altitude as quickly as possible after take-off, so if there is an engine problem they have time to find a landing place.\n\nIf thrust is lost, gravity and lift become unbalanced with gravity winning because altitude must be lost to maintain airspeed.  drag wins over thrust since there isn't any thrust so altitude must be lost to compensate for drag-thrust imbalance.\n\nsource: i'm a pilot
699136
Once birds get up in the air, they use two main flying techniques to stay up there.\n\nSoaring: When birds soar, they take advantage air currents to help hold them up. Three kinds of air currents are especially helpful to soaring birds. \n\nThermal air currents develop in places where the air is warmer in one spot than an adjoining area, such as a paved road alongside a snowy field. Even on a very cold day, the sun will heat the pavement at least a few degrees more than the snow. This slightly warmer air is slightly lighter than the colder air, and rises. This rising air current can lift very light objects, like feathers and hollow bones. The birds that most often take advantage of thermals (like the hawks that fly along coastlines) usually have very wide wings and tail. This makes the area of their wings very large compared to their body weight. \nUpdrafts, also called obstruction currents, develop when wind hits an obstruction, like a cliff or a building. The rushing air has to go somewhere, so it goes up, and can carry a bird up with it. Birds who fly on updrafts (like the many hawks that migrate along Hawk Mountain, Pennsylvania) also have very wide wings and tail. \nWind moving toward a bird with spread wings can hold the bird up, thanks to the airfoil shape of the wings. Birds that fly on moving air currents often have long, narrow wings, such as gulls and albatrosses. \n  \n \nFlapping: When birds flap, the stroke of their downbeat moves the wing tips forward and downward. The wingtips make a loop at the bottom of the downstroke, and as the wings move up, the wing tips move upward and backward. In the downstroke, the pressure is higher below the wing than above, causing lift. And as they move forward, the rush of air on their airfoil wings causes more lift. But because flapping birds have smaller wings than soaring birds, they must move forward faster to stay in the air. Most songbirds must fly at least 11 miles per hour to stay up. One scientist calculated that for an ostrich to stay aloft, it would have to take off and maintain a minimum speed of 100 miles per hour. Birds who use their wings to flap more than soar often have smaller wings than soaring birds.
497390
No, we couldn't fly if we had wings. We're much to heavy for one thing. Flying birds have hollow bones and many other adaptations for flight (like a "keel" on their breastbone that the flight muscles attach to and specialized respiratory systems). It's a good thing we're smart enough to make things like planes, because that's the only way we're getting in the air.
972802
They fly because of Bernoulli's theroem, which states that a moving gas has a lower pressure than a stationary one.  The wing has a curve across the top, and a flat underside.  That means that air going over the top has to move faster than the air going under the wing, which creates a lower pressure area on top of the wing.  The higher air pressure under the wing pushes up on the wing.\n\nYou can experience something similar by putting your finger over the jet in a jacuzzi.  If you hold it close to the opening, the fast moving water flowing around your finger will have a lower pressure than the surrounding water, and you will feel a slight pull on your finger towards the jet.  Move your finger back a little, and you will feel the weight of the water hitting your finger and pushing it away.\n\nAs far as balancing the plane, the fuel is moved around just like transparentearth said, and the manufacturer of the plane has carefully calculated where the center of gravity of the plane is, and the pilots have detailed information about how the load the plane is carrying should be distributed.
51813
Your question is too wide to be answered easily in one sitting.  So I'll look at how and why of aerodynamics (simply) and then answer the speed bit.\n\nThis a bit of material I wrote for flight cabin staff to help them understand these principles.\n\nLift is the aerodynamic force that counteracts gravity and holds an airplane in the air. Most of the lift required by an airplane is created by its wings, but a certain portion is also generated by other parts of the aircraft, such as the fuselage. But what actually causes the lift to be created?\nAir is a fluid, just like water. Lift can only be generated when a fluid is in motion. For example, a wing must be passing through the air or the air must be moving around a stationary wing, one or the other. (The way it usually happens is that the wing is doing most of the moving, although the air may be moving, at the same time.)  The wing is moved through the air by the thrust generated by the aircraft’s engines.\n\nMost aircraft wings have a special, basic shape as viewed edge-on: The upper surfaces are curved and their lower surfaces are flatter. This shape is what works with the fluid motion of the air to create lift. As air moves around a wing, some goes over the top and some goes underneath. The air that goes over the curved upper surface undergoes two important changes: it is reduced in pressure and it is accelerated downward (as it leaves the trailing edge of the wing). The wing is forced up into the region of reduced air pressure above the upper surface of the wing by the higher air pressure beneath the wing. Also, the downward acceleration of the air (downwash) at the trailing edge forces the wing upward.\n\nSo this is the basis of aerodynamics.  Roraty wing aircraft (helicopters) work on the same basis, the aerofoil is rotated and lift created by the rotors (moving aerofoils). The thrust to move the aircraft forward is produced by tilting the rotor head, in the direction required.  Hence it can move forwards, sideways and backwards.  But the explanation would take a separate large answer.\n\nAs for speed, the maximum forward speed of the aircraft is determined by the thrust available, but the aircraft is limited by the design of the wing, the wing shape for a low speed high lift glider is very different to that of a supersonic aircraft.  The lowest speed is really controlled by the wing.  As the aircraft sppeed reduces so does the speed of the flow over the wing, surface friction slows it down further until the air refuses to flow over the aerofoil and it breaks up into turbulence and all lift is lost.  A number of things can be done to get this point at which the lift is lost (stall) at the lowest speed possible - such as flaps, slats etc (but this is another long answer).  On helicopters there is no slowest speed as the aircraft will just hover when it stops moving forward, but its maximum forward sppeed is limited by the air over the blades going sonic and loosing lift, and problems with the trailing blade (the one that is heading towards the back of the helicopter in forward flight.) Again another long answer.\n\nHope that helps.  The book below is the RAF's bible on aerodynamics.