Question

(AS-100:C1L1:LQ8) Which phenomenon is known as the Bernoullian lift?

The air flow over the top of the wing causing the pressure to drop and the wings to move upward
For every action, there is an equal and opposite reaction
The additional lift noticed when a pilot angles the wing of the plane up against an oncoming wind
There is no relationship between pressure and fluids in motion.
OO
a
b
с
d

Answer 1

The correct statement is, the air flow over the top of the wing causing the pressure to drop and the wings to move upward.

Step-by-step explanation:

The phenomenon known as the "Bernoullian lift" is associated with the way airflow over the top of a wing causes the pressure to drop, resulting in upward force on the wing. In answering this question, I will explain which of the provided statements corresponds to the Bernoullian lift and clarify the relationship between pressure and fluid flow that characterizes this phenomenon.

`\hrulefill`

Bernoullian lift is correctly described by the statement: "The air flow over the top of the wing causing the pressure to drop and the wings to move upward." This principle can be understood by Bernoulli's equation, which relates the speed of a fluid to its pressure. According to this principle, as the speed of the air increases over the top surface of the wing, the pressure above the wing decreases. The higher pressure beneath the wing then pushes the wing upward, which is what we observe as lift.

The other options given have the following relevance to flight and lift:

• "For every action, there is an equal and opposite reaction" is Newton's third law of motion. While it also explains part of the lift produced by wings (since the wing pushes air down and the reaction pushes the wing up), it is not termed "Bernoullian lift."

• "The additional lift noticed when a pilot angles the wing of the plane up against an oncoming wind" is describing the increase in lift due to an increase in the angle of attack. This is a dynamic lift which is a different concept and depends on the angle at which the wing meets the oncoming air.

• "There is no relationship between pressure and fluids in motion" is an incorrect statement and does not describe any lift-related phenomenon. In fact, the relationship between pressure and fluid motion is foundational to understanding Bernoullian lift.

`\hrulefill`

Additional Information:

Bernoulli's Principle: A fundamental principle of fluid dynamics which states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.

`\boxed{\left\begin{array}{ccc}\text{\underline{Bernoulli's Principle:}}\\\\P_1 + (1)/(2) \rho v_1^2 + \rho gh_1 = P_2 + (1)/(2) \rho v_2^2 + \rho gh_2 \end{array}\right}`

Where:

• ρ = fluid density
• g = acceleration due to gravity
• P₁ = pressure at elevation 1
• v₁ = velocity at elevation 1
• h₁ = height of elevation 1
• P₂ = pressure at elevation 2
• v₂ = velocity at elevation 2
• h₂ = height at elevation 2

Lift: A force generated by the differential pressure between the upper and lower surfaces of a wing. Lift is essential for an aircraft to achieve and maintain flight.

Angle of Attack: The angle between the chord line of the wing and the direction of the oncoming air (relative wind).

Fluid Dynamics: The study of how fluids (liquids and gases) move and the forces on them. It includes the study of Bernoulli's principle and its applications.