Question

The weight of an aeroplane flying in the air is balanced by

A) A vertical component of the thrust created by the air current striking the lower surface of the wings.
B) Force due to reaction of gasses ejected by the revolving propeller
C) Upthrust of the air, which will be equal to the weight of the air having the same volume as the plane.
D) Force due to the pressure difference between the upper and lower surface of the wings created by the difference air speeds on the surface

Answer 1

According to Newton's third law of motion, thrust is the reaction force. Newton’s third law of motion states that every action has an equal and opposite reaction. Equal and opposite reaction means, the reactive force is equal in magnitude and opposite in direction.

Step by step solution:

According to the question it is given that the weight on an aeroplane flying in the air is balanced.

The structure of the airplane has special types of the construction. It is maintained such that the upper surface of the wings is curved more. The lower surface of the wings is curved less. This causes the speed of the air above the wings is more and the speed of the air below the wings is lesser.

So, here we can apply Bernoulli's theorem to get the exact situation.

The pressure of the air with more speed is less, and the pressure exerted by the slower air is more.
So, the pressure below the wings is greater than that of above the wings.

The pressure difference observed on both sides of the wings produced vertical lift on the aeroplane.

So, from the above explanation it is concluded that the weight of an aeroplane flying in the air is balanced by the vertical component of the thrust created by the air current striking the lower surface of the wings.

Hence, the correct option is A.

Note:
Bernoulli’s principle is applied on the fluid flowing through the pipe having different diameters at different points. It is given as:
${P_1} + \dfrac{1}{2}\rho v_1^2 + \rho g{h_1} = {P_2} + \dfrac{1}{2}\rho v_2^2 + \rho g{h_2}$
The difference in the speed of the field is caused by the different diameter.