Newton’s third law of motion states that, for every action, there is an equal and opposite reaction. Based on this law, wings are forced upwards because they are tilted, pushing air downwards so the wings get pushed upwards. This is the angle of attack or the angle at which the wing meets the airflow.
As air flows over the surface of a wing, it sticks slightly to the surface it is flowing past and follows the shape. If the wing is angled correctly, the air is deflected downwards. The action of the wing on the air is to force the air downwards while the reaction is the air pushing the wing upwards. A wing’s trailing edge must be sharp, and it must be aimed diagonally downwards to create lift. Both the upper and lower surfaces of the wing act to deflect the air.
The amount of lift depends on the speed of the air around the wing and the density of the air. To produce more lift, the object must speed up and/or increase the angle of attack of the wing (by pushing the aircraft’s tail downwards).
Speeding up means the wings force more air downwards so lift is increased. Increasing the angle of attack means the air flowing over the top is turned downwards even more and the air meeting the lower surface is also deflected downwards more, increasing lift. There is a limit to how large the angle of attack may be. If it is too great, the flow of air over the top of the wing will no longer be smooth and the lift suddenly decreases.
Birds and planes change their angle of attack as they slow to land. Their angle of attack is increased to ensure their lift continues to support their weight as they slow down. Wings and tails need to be movable so that their shapes can be changed to control their flight.
