The lift on an aeroplane wing arises because

  • A. air moves faster over the curved upper surface, lowering the pressure there
  • B. air moves faster under the wing
  • C. the wing is lighter than air
  • D. the engines push the wing upwards

Explanation

The aerofoil shape makes the air travel further and faster across the top, so by Bernoulli's principle the pressure above is lower than below and the difference multiplied by the wing area gives the lift. The wing also deflects air downwards, and by Newton's third law that contributes lift as well. Both descriptions are valid ways of accounting for the same force.

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