"How do planes fly?" Return to list of pracs

Aim: This activity is used to demonstrate the way the wings on a plane hold the plane up in the air.

Equipment: The equipment includes...  

Method: Hold the piece of paper at two corners between your thumbs and pointing fingers. Hold the paper up just under your lip along one edge. Blow hard across the top of the paper as hard as you can with a narrow "jet" of breath.

Results: The piece of paper will flap around but will generally rise in the air.

Background knowledge: Fast moving air produces low air pressure. This means that the fast moving particles of air are further apart from each other compared to slower moving air particles. When there is less air particles pressing down on top of the paper (due to low air pressure) and more air particles pressing upwards from underneath (due to higher air pressure), the paper will tend to rise upwards.

The wing on any plane is shaped so that the top of the wing is curved and the bottom is flatter. As a result, air has to travel further (and faster!) to get around the top of the wing compared to the bottom which is flatter. This results in lower air pressure on top and higher underneath: ie. more force upwards and less downwards ie. the wing is pushed upwards and supports the whole plane in the air. The faster the plane goes, the more force holds the plane in the air.