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What makes a plane go up?

What makes a plane go up? Air. A plane flies through the air by continually pushing and pulling the surrounding air downward. In response to the force of moving the air down, the air pushes the airplane upward. Newton's 3rd law of motion states that for every action there is an equal and opposite re-action. An airplane wing is shaped so that the air is deflected downward as the wing passes. Because air is a fluid (a gas), both the top and the bottom surface of the wing deflect the air. This is very different than dealing with solid pellets for which only the bottom surface would deflect. The faster an airplane travels the more lift is generated. Inclining the wing to the wind also produces more deflection and more lift. The wings of an airplane have adjustable flaps that can be extended or retracted. When extended, the flaps increase the deflection of the air and provide greater lift for takeoff and landing.

As it flies, a plane is in the center of four forces. Lift (upward force) and thrust (forward push, provided by a propeller) get a plane into the air. Gravity and drag (air resistance, which is friction caused by air rubbing against the plane) try to pull the plane down and slow its speed. A plane must be built so that lift and thrust are stronger than the pull of gravity and drag by just the right amount. Lift from the wings is used to overcome the force of gravity. Shape is important in overcoming drag. For example, the nose of a plane is rounded so it can push through the air more easily. The front edge of each wing is rounded too. An airplane built like a railroad boxcar just wouldn't fly very well.

Return to Lesson #9

Related Pages:
Is Air Something? Index
Aeronautics Activities
Aerospace Activities Page
Aerodynamics Index


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Editor: Tom Benson
NASA Official: Tom Benson
Last Updated: May 13 2021

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