Question

In a test experiment on a model aero plane in a wind tunnel, the flow speeds on the
upper and lower surfaces of the wing are 70 m s-1 and 60 m s-1 respectively. The
area of the wing is 2.4 m and density of air 1.3 kg m-3. The lift on the wing of the
plane is
(A) 1014N
(C) 2315N
(B) 2028N
(D) 1645N​

Answer 1

Answer:

B

Explanation:

Speed of wind on the upper surface of the wing, V1 =70m/s

Speed of wind on the lower surface of the wing, V2 =60m/s

Area of the wing, A=2.4m²

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×(70²-60²)×2.4

Therefore, the lift on the wing of the aeroplane is 2028N