Question

A plane is in level flight at constant speed and each of its two wings has an area of 40 m2 . If the speed of the air is 180 km/h over the lower wing surface and 252 km/h over the upper wing surface, the mass of the plane is ________kg. (Take air density to be 1 kg m–3 and g = 10 ms–2

Answer 1

Given:

$A = 80 \, \text{m}^2$

Using Bernoulli’s equation:

$\Delta P = (P_2 - P_1) = \frac{1}{2} \rho (V_1^2 - V_2^2)$

Area of wings = $A$

Calculating the lift force:

$mg = \frac{1}{2} \times 1 \times (70^2 - 50^2) \times 80$

Simplifying:

$mg = 40 \times 2400$

$m = 9600 \, \text{kg}$