An aerofoil is mounted in a wind-tunnel so that air streams past its upper and lower surfaces with different speeds.
Answer the following questions about the physical origin of the upward force acting on the aerofoil.
(i) Explain why a difference in the speeds of air over the two surfaces produces a difference in static pressure between them.
(ii) Describe qualitatively how increasing the angle of attack of the aerofoil affects the magnitude of the upward force.
(iii) Name any two design features of a wing that enhance this upward force and justify your choices in terms of air-flow behaviour.