Question

Air of density $1.2\, kg\, m^{-3}$ is blowing across the horizontal wings of an aeroplane in such a way that its speeds above and below the wings are $150\, ms^{-1}$ and $100\, ms^{-1}$, respectively. The pressure difference between the upper and lower sides of the wings, is :

• A. $60\, Nm^{-2}$
• B. $180\, Nm^{-2}$
• C. $7500\, Nm^{-2}$
• D. $12500\, Nm^{-2}$

Answer 1

Answer: (C)

Pressure difference
$P_{2}-P+_{1}=\frac{1}{2}\rho\left(v^{2}_{2}-v^{2}_{1}\right)$
$=\frac{1}{2}\times1.2\left(\left(150\right)^{2}-\left(100\right)^{2}\right)$
$=\frac{1}{2}\times1.2\left(22500-10000\right)$
$=7500\,Nm^{-2}$