more rapidly over its upper surface than over its lower surface. As a result, the air above the wing travels at an increased speed, producing a region of reduced pressure. The pressure below the wing, which is therefore greater, exerts an upward force, or lift, on the wing.LiftLift is the third factor in which physics aids the flight of an aircraft. Lift is influenced by a variety of different things, such as area, tilt of the wing, and on the speed of the aircraft. Wing area influences lift; the more of the wing that is exposed to the air, the greater the lift. The up or down tilt of the wing, usually called its angle of attack, contributes to or detracts from lift. As a wing is tilted upward, that is, as its angle of attack is increased, its lift increases. The air passing over the top of an uptilted wing must travel a greater distance and thus produces a greater pressure differential between the upper and lower surfaces. Airplane speed has a great influence on lift. The faster the air moves over and under the surfaces of an airplane, the greater the pressure differential and, as a result, the greater the lift. As an airplane flies on a level course, the lift contributed by the wing and other parts of the structure counterbalance the weight of the plane. Within certain limits, if the angle of attack is increased while the speed remains constant, the plane will rise. If the angle of attack is decreased, that is, the wing is tilted downward, the plane will lose lift and start to descend. An airplane will also climb from level flight if its speed is increased, and it will dive if its speed is decreased. Lift varies directly with speed.DragDrag is another factor which is contributed by the flight of an airplane. Drag is the force that tends to retard the motion of the airplane through the air. Most drag is a result of the resistance of the air to objects moving through it. This type of drag can be reduced by streamlining the aircraft. It...
