Flight has fascinated humans for centuries. How does a massive aircraft weighing hundreds of tons stay in the air? The answer lies in understanding four fundamental forces that act on every aircraft during flight. These forces are lift, which acts upward; weight or gravity, which pulls downward; thrust, which propels the aircraft forward; and drag, which opposes motion. When these forces are properly balanced, with lift overcoming weight and thrust overcoming drag, flight becomes possible.
Lift generation is the key to flight and involves two fundamental principles working together. First, Bernoulli's principle explains that as air flows over the curved upper surface of the wing, it must travel faster than the air flowing under the flatter lower surface. This faster-moving air creates lower pressure above the wing compared to below it. Second, Newton's third law comes into play as the wing deflects air downward. According to this law, for every action there is an equal and opposite reaction, so when the wing pushes air down, the air pushes the wing up with an equal force. These two effects combine to generate the upward force we call lift.