Air flows over and under the wings of an aeroplane as it moves forward. The wings are designed to make the air travelling over the top surface move faster than the air moving below the wing, and this has the effect of lifting the wing up.

In order to understand more about how the the air moves around the wing we have to think about ideas of air flow and turbulence, and also how the forces acting on an aerofoil can be represented in terms of components and plotted as graphs.

The most difficult ideas are concerned with understanding how the air flows just as the wing starts to move, and for these you have to think of air as a fluid having viscosity.