Q 11-09-068JEE MainJEE Main 2024 (29 Jan, Shift 1)Easy
In a test experiment on a model aeroplane in a wind tunnel, the flow speeds on the upper and lower surfaces of the wings are $70\ \text{m s}^{-1}$ and $65\ \text{m s}^{-1}$ respectively. If the wing area is $2\ \text{m}^2$, the lift of the wing is ______ N. (Given density of air $= 1.2\ \text{kg m}^{-3}$)
Numerical value type. Enter your answer.
Answer: 810
By Bernoulli's theorem, the pressure difference is
$$\Delta P = \frac12\rho(v_1^2 - v_2^2) = \frac12\times1.2\times(4900 - 4225) = 405\ \text{Pa}$$
$$\text{Lift} = \Delta P\times A = 405\times2 = 810\ \text{N}$$
Solution by Sreeraj P, M.Sc Physics