4 ms·

I have seen many examples of this incorrect explanation in textbooks and posters. It boggles the mind how it has survived for so long. I actually shockingly saw

by hristov 16y ago

I have seen many examples of this incorrect explanation in textbooks and posters. It boggles the mind how it has survived for so long. I actually shockingly saw the same incorrect explanation in one episode of NOVA (yes it has gone downhill). The biggest problem with this diagram is that the air leaving the wing is horizontal, which is (a) wrong and (b) really screws up a kid's understanding of Newton's laws. If the diagram correctly showed the air being forced down by the wing, then a kid could figure out that the wing creates a downward force on the air and the air creates an equal and opposite upward force on the wing.

borism 16y ago
It seems to me it's you who got things wrong. Explanation about wing forcing air down is very VERY wrong.
- ajuc 16y ago
  Then how is momentum preserved?
- hristov 16y ago
  How so? The wing has to exert a downward force on something if it wants to go up? If not air then what ?
  - borism 16y ago
    the lift comes from pressure differential between "top" and "bottom" surface of the wing - that's the definition used by professionals in the field. Here's why definition about deflection of the air is generally not accepted: http://en.wikipedia.org/wiki/Lift_(force)#Criticisms_of_deflection.2Fturning http://en.wikipedia.org/wiki/Lift_(force)#Criticisms_of_defl...
    - hristov 16y ago
      The link you provided does not support what you are saying. The link you provided actually agrees with me saying that the theory about air being deflected down is correct. It merely says that while correct, this explanation is not rigorous enough to do engineering. Which is totally right. But I was not trying to do any engineering, I was trying to provide a simple explanation about how a wing works and how that relates to Newton's third law of motion.
      - borism 16y ago
        I'm glad that you found yourself vindicated and will refrain from interfering with your righteousness.

by hristov 16y ago

borism 16y ago

It seems to me it's you who got things wrong. Explanation about wing forcing air down is very VERY wrong.

ajuc 16y ago
Then how is momentum preserved?
hristov 16y ago
How so? The wing has to exert a downward force on something if it wants to go up? If not air then what ?
- borism 16y ago
  the lift comes from pressure differential between "top" and "bottom" surface of the wing - that's the definition used by professionals in the field. Here's why definition about deflection of the air is generally not accepted: http://en.wikipedia.org/wiki/Lift_(force)#Criticisms_of_deflection.2Fturning http://en.wikipedia.org/wiki/Lift_(force)#Criticisms_of_defl...
  - hristov 16y ago
    The link you provided does not support what you are saying. The link you provided actually agrees with me saying that the theory about air being deflected down is correct. It merely says that while correct, this explanation is not rigorous enough to do engineering. Which is totally right. But I was not trying to do any engineering, I was trying to provide a simple explanation about how a wing works and how that relates to Newton's third law of motion.
    - borism 16y ago
      I'm glad that you found yourself vindicated and will refrain from interfering with your righteousness.