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 70 m s–1 and 63 m s-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
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 Densityof air, ρ=1.3kg/m3 According to Bernoullis theorem, we have the relation: P1+(1/2)ρ(V12)=P2+(1/2)ρ(V22) P2−P1=(1/2)ρ(V12−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 =(1/2)ρ(V12−V22)A =(1/2)1.3[702−632]2.5 =1512.87 N=1.51×103 N Therefore, the lift on the wing of the aeroplane is 1.51×103 N.
