Question

# In a test experiment on a model aeroplane in a wind tunnel, the flow speeds on the upper and lower surfaces of the wing are 70ms–1 and 63ms–1 respectively. What is the lift on the wing if its area is 2.5 m2? Take the density of air to be 1.3 kg m–3.

Solution

## Speed of wind on the upper surface of the wing, V1=70m/s Speed of wind on the lower surface of the wing, V2=63m/s Area of the wing, A=2.5m2 Density of air, ρ=1.3kgm–3 According to Bernoulli’s theorem, we have the relation: P1+12ρV21=P2+12ρV22P2−P1=12ρ(V21−V22) Where, P1 = Pressure on the upper surface of the wing P2= Pressure on the lower surface of the wing The pressure difference between the upper and lower surfaces of the wing provides lift to the aeroplane. Lift on the wing =(P2−P1)A =12ρ(V21−V22)A=121.3((70)3−(63)2)×2.5 =1512.87 =1.51×103N Therefore, the lift on the wing of the aeroplane is 1.51×103N.

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