Question

Aerofoils are so designed that the speed of air

• A. on top side is more than that on lower side
• B. on top side is less than that on lower side
• C. is same on both sides
• D. None of the above

Answer 1

The correct option is A on top side is more than that on lower side

The aerofoils are so designed that,
$P_{\text{upper side}}<P_{\text{lower side}}$
so that the aerofoils get a lifting force in upward direction.
According to Bernoulli's theorem, where the pressure is large, the velocity will be less and vice-versa.
Thus,
$v_{\text{upper side}}>v_{\text{lower side}}$