explanation homework (3rd assignment)

Explanation text (3rd ASSIGNMENT OF GENRE BASED WRITING TEXT)
ILIMA FITRI AZMI
2201408111
GBW 307-308

How do airplanes fly?

An airplane is a vehicle which is able to fly by being supported by the air, or in general, the atmosphere of a planet. An airplane counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.
An airplane flies because air moving over and under its surfaces, particularly its wings, travels at different velocities, producing a difference in air pressure, low above the wing and high below it. The low pressure exerts a pulling influence, and the high pressure a pushing influence. The lifting force, usually called lift, depends on the shape, area, and tilt of the wing, and on the speed of the aircraft. The shape of the wing causes the air streaming above and below the wing to travel at different velocities. The distance over which the air must travel above the curved upper surface forces that air to move faster to keep pace with the air moving along the flat lower surface.
Essentially there are 4 aerodynamic forces that act on an airplane in flight; these are lift, drag, thrust and gravity (or weight).In simple terms, drag is the resistance of air (the backward force), thrust is the power of the airplane's engine (the forward force), lift is the upward force and gravity is the downward force. So for airplanes to fly, the thrust must be greater than the drag and the lift must be greater than the gravity (so as you can see, drag opposes thrust and lift opposes gravity).This is certainly the case when an airplane takes off or climbs. However, when it is in straight and level flight the opposing forces of lift and gravity are balanced. During a descent, gravity exceeds lift and to slow an airplane drag has to overcome thrust. The thrust is generated by the airplane's engine (propeller or jet), gravity is a natural force acting upon the airplane and drag comes from friction as the plane moves through air molecules. Drag is also a reaction to lift, and this lift must be generated by the airplane in flight. This is done by the wing of the airplane.