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The flow speed of air above the aircraft wing is v1 and below the aircraft wing is v2, then which of the following is correct for the dynamic lift of the aircraft?

The flow speed of air above the aircraft wing is v1 and below the aircraft wing is v2, then which of the following is correct for the dynamic lift of the aircraft? Correct Answer v<sub>1</sub> &gt; v<sub>2</sub>

CONCEPT:

Dynamic lift:

  • Dynamic lift is the force that acts on a body, such as an airplane wing, a hydrofoil, or a spinning ball, by virtue of its motion through a fluid.
  • In many games such as cricket, tennis, baseball, or golf, we notice that a spinning ball deviates from its parabolic trajectory as it moves through air.
  • This deviation can be partly explained on the basis of Bernoulli’s principle.

Aerofoil or lift on aircraft wing:

  • Figure c shows an aerofoil, which is a solid piece shaped to provide an upward dynamic lift when it moves horizontally through the air.
  • The cross-section of the wings of an airplane looks somewhat like the aerofoil with streamlines around it.
  • When the aerofoil moves against the wind, the orientation of the wing relative to flow direction causes the streamlines to crowd together above the wing more than those below it.
  • Therefore the flow speed on top is higher than that below it.
  • Thus an upward force resulting in a dynamic lift of the wings and this balances the weight of the plane.

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EXPLANATION:

Given v1 = the flow speed of air above the aircraft wing, v2 = the flow speed of air below the aircraft wing

  • The cross-section of the wings of an airplane looks somewhat like the aerofoil with streamlines around it.
  • When the aerofoil moves against the wind, the orientation of the wing relative to flow direction causes the streamlines to crowd together above the wing more than those below it.
  • Therefore the flow speed on top is higher than that below it.
  • So we can say that for the dynamic lift of the aircraft,

⇒ v1 > v2

  • Hence, option 1 is correct.

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