The Forces Acting Upon A Plane
Lift is the result of the air pressure on the top and bottom of the wings that causes the air to push upwards on the wings, therefore pushing the plane up. For this to happen, air has to be flowing, which is why airplanes cannot rise vertically. Lift has been around as an idea since the early 1700's, though they didn't have the pressure differencial science down and though of it more of a force that caused wind to blow up from the ground. The other way life can be achieved is using hot air (which rises) in a contained area to push the object up, much like how a hot air balloon functions. If there is not enough lift, the plane would go nose first towards the ground, and crash unless enough lift was produced. This is similiar to stalling, when there is no lift at all.
Whereas lift causes the plane to get higher in the sky, gravity pulls all object towards the ground and the center of the nearest dense object Sir Isaac Newton gave gravity its theory and explained how it worked as a force. The basics of gravity is that every object has a certain pull that is related to the objects mass and/or density, that will pull other, smaller objects towards it. For example, this force is what keeps the earth circling the sun, and the moons of planets in orbit. Since the earth is so much more massive than planes flying over its surface (along with all other objects on Earth) that the earth's gravity is pulling on these objects, which keeps our feet planted firmly on the ground, whereas planes have the lift needed to escape this force somewhat, allowing them to fly further off the earths surface.
Drag is the force of the air pushing back upon an object traveling, and can be seen when it is windy outside and a person has to lean into the wind to make walking easier. The airplane, as it travels through the air, is being pushed on by the air it is surronded by, causing drag. Drag can be reduced in many ways, including using a smooth surface, special paints, a spherical or rounded front or parts, and less surface area. Drag can reduce speeds and gas efficiency, which makes it an important aspect to consider when making an airplane. This force affects every object traveling at all speeds, and has been known to down planes and cause large amounts of turbelence when the air pattern is uneven.
Thrust is the force that pushes a plane forward, and is the counter force to drag. Engines use on average 48,445 gallons of gas at maximum capacity, using that up at a rate of about 1 gallon per second to produce enough thrust to lift the behemoth into the air and keep it from crashing into the ground below. Immense amount of research goes into finding ways to make safer and more efficient engines, to promote even more use of the airplane industry. Most airplane engines come in at around 400 lbs, with most of the engines function to be making the thrust for the plane, with a small part devoted to maintaining cool temperatures.