Teaching Lift to Seventh Graders

But the Newtonian force to shove the air down comes from a pressure
difference. The only way to shove air anywhere is by creating a pressure
gradient field.

I wrote an article in Kitplanes several years ago showing that the two
amount to the same thing. Parts of this article are extracted on my web
site.

Pure Newtonian lift only comes at very high altitude where mean free
path is equal to or larger than wing chord. Newton himself realized this
and warned people not to use his lift derivation for designing flying
machines that flew in normal atmosphere.

-- 
Don Stauffer in Minnesota
[EMAIL PROTECTED]
webpage- http://www.usfamily.net/web/stauffer