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When looking at the cross section of a wing, I have always said that the
air flow under the wing (which is a relatively flat surface) is slower
than the air flow over the top of the wing which is curved. The
question from them is "why isn't it just as likely that he air over the
top of the wing does not speed up and simply takes a longer time to
travel the longer distance over the curved section of the wing?".
Let's look at 2 particles, one goes over the wing, and one goes
under. If the one going under the wing goes faster (shorter distance
and shorter time) it gets to the end of the wing first, while the
other particle is still over the top of the wing.
This makes the next 2 particles do the same. After a while the
particles will 'back up' on top of the wing. If that were the case,
the density would have to become greater over the wing, pushing down
more on the wing, and it would not fly!
This sounds reasonable, but then I always wondered how certain planes can
fly upside-down. Are the wings on these planes shaped differently?
While I truly appreciate the website/book given as a reference -- I think
it would be a bit much for my Algebra-based students or High School
students. :^)
If you want a good website for those target audiences, that also have good
dynamic simulations for use on a SmartBoard or other projection system,
take a look at:
http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html