Teaching Lift to Seventh Graders

>> I don't think there's any real debate, unless it involves lift demons.
>> The physics-based way lift works is that the wing shoves the air down.
> 
> Does it?  How about in something like:
> 
> http://www.aether.demon.co.uk/coolkit/graphics/ekranoplan/antishipping.jpeg
> 
> ?

It's still the same priciple: Basic Newtonian action and reaction.  
The difference here is that the air that has been "shoved down" 
by the wing has another surface to interact with ("ground effect"), 
which results in a modified flow-field around the wing that significantly
increases its efficiency at "shoving air down" --- and more importantly, 
an =ENORMOUS= reduction in the induced drag, because the interaction 
of the two counterrotating wingtip vortices with the ground causes 
them to move toward each other and cancel each other out a relatively 
short distance behind the plane. (See also
<http://www.av8n.com/how/htm/airfoils.html#sec-induced-drag>,
<http://www.av8n.com/how/htm/airfoils.html#sec-soft-field-why>, 
which provides a heuristic motivation of the favorable consequences 
of the "ground-effect" interaction using the "method of images:" 
an aircraft in the ground effect regime "sees" an additional induced
airflow generated by an "image" of itself in the ground, increasing 
its lift while canceling much of its induced drag.)


-- Gordon D. Pusch