ace wrote:

Would this be true for different atomospheric pressures? Is this a
rough rule of thumb? I dont see how there can be such a tidy formula
for something as variable as air. what if air was replaced by carbon
dioxide.


The formula applies for any gas, any density. Check any book on fluid mechanics
or aerodynamics or Wikipedia: http://en.wikipedia.org/wiki/Drag_%28physics%29.

Mike