‘Lift’

Aircraft

Aircraft in flight

Aircraft

Aircraft

Aircraft in flight

Enlarge image

Why do aeroplanes not get pulled down to the ground by gravity? After all they do not have water to push them up! All they have to push them up is air. Now air would not hold you or me up. So what is the difference?

For air to hold a plane up you have to have moving air. The faster the air the lower the pressure. The air that goes over the curved wing of the plane has to go faster than the air that goes under the wing, so the higher pressure from underneath the wing pushes upwards and keeps the plane up. This is called lift.

A helicopter stays up without moving because the rotor blades whirling around give the upward force.