Question

An aeroplane of mass $6000kg$ is flying at an altitude of $3km$. If the area of the wings is $30m^2$ and the pressure at the lower surface of wings is $0.6\times {10}^{5}pa$, the pressure on the upper surface of wings is : ( in pascal) ( $g=10m{s}^{-2}$)

• A. $5.8\times {10}^4$
• B. $6.8\times {10}^4$
• C. $7.8\times {10}^4$
• D. $8.8\times {10}^4$

Answer 1

Answer: (A)

$5.8\times {10}^4$

Pressure at lower surface of wing$=0.6\times {10}^{5}Pa$
Let pressure at upper surface of wing$=p$
Weight of the airplane $=5\times {10}^{4}N$
For equilibrium, Weight $=$upthrust due to air
$\Rightarrow 5\times {10}^4=(0.6\times {10}^5-p)\times 50$
$\Rightarrow {10}^3=0.6\times {10}^5-p$
$\Rightarrow p=0.6\times {10}^5-{10}^3$
$\Rightarrow p=59\times {10}^{3}Pa$