In a test experiment on a model aeroplane in wind tunnel, the flow speeds on the upper and lower surfaces of the wings are 70 m s - 1 and 65 m s - 1 respectively. If the wing area is 2 m 2 , the lift of the wing is _______ N . (Given density of air = 1 . 2 kg m - 3 )

Step-by-step solution

Applying Bernoulli's principle on upper & lower surfaces, we get P 1 + 1 2 ρ v 1 2 + ρ g h 1 = P 2 + 1 2 ρ v 2 2 + ρ g h 2 Since, height difference between upper and lower surface is negligible. ⇒ P 2 - P 1 = 1 2 ρ v 1 2 - 1 2 ρ v 2 2 Therefore, upthrust acting due to pressure difference: ⇒ F A = 1 2 ρ v 1 2 - v 2 2 ⇒ F = 1 2 × 1 . 2 × 70 2 - 65 2 × 2 = 810 N