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Difficulty: EasyFluid Dynamics and Bernoulli's Principle

During flight, an aircraft wing (airfoil) is designed so that air travels significantly faster over its curved upper surface compared to its flatter lower surface. According to Bernoulli's principle, what is the result of this difference in air velocity?

  1. The static pressure above the wing becomes lower than the pressure below it, generating upward lift.Answer
  2. B
    The faster-moving air above the wing generates higher static pressure, which pulls the aircraft upward.
  3. C
    The difference in air speed creates a buoyant force based on the displaced weight of the air, lifting the wing.
  4. D
    The faster air over the top of the wing compresses tightly, increasing its density and pushing the wing upward.

Answer

The static pressure above the wing becomes lower than the pressure below it, generating upward lift.
According to Bernoulli's principle, as the velocity of a fluid (such as air) increases, its static pressure decreases. Because the wing is shaped to make the air travel faster over its top surface, a region of low pressure is created above the wing. The slower-moving air beneath the wing maintains a relatively higher pressure. This difference in pressure—high on the bottom, low on the top—results in a net upward force that lifts the aircraft.

Step-by-Step Solution

1
Recall the fundamental rule of Bernoulli's principle regarding fluid flow.
In a flowing fluid, an increase in velocity is accompanied by a decrease in static pressure.
This inverse relationship is the core concept of Bernoulli's principle.
2
Apply the principle to the specific scenario of the aircraft wing described in the question.
The air moving over the top of the wing has a higher velocity than the air moving underneath. Therefore, the static pressure on the top surface must be lower than the static pressure on the bottom surface.
Mapping the physical conditions (faster top, slower bottom) to the principle reveals the pressure distribution.
3
Determine the physical consequence of this pressure difference.
The relatively higher pressure beneath the wing pushes upward toward the area of lower pressure above the wing, creating a net upward force known as lift.
Objects are naturally pushed from areas of higher pressure toward areas of lower pressure.

Key Concept

According to Bernoulli's principle, an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure. This pressure differential across surfaces like airfoils creates mechanical forces such as lift.
Estimated Time:45s
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Topics

Fluid Dynamics and Bernoulli's Principle

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