I must be stupid

[Z!re]

http://goddess.selfip.com/random/series/TMU/

Interessting series about various stuff, made in 1985

[SJ Zero]

Kelly, of course, we're only talking about a problem in kinematics here, not dynamics.

If you wanted to, however, you could replace the constant A with a formula which calculates the opposing force relatively accurately by simply pushing against gravity with the force of air pressure generated by moving through the air, probably using bernoullis energy equations (h = v^2/2g, P = Rho * G * h, F = P * Area). After that you'd have to do some voodoo to factor V into something useful, of course, and the unfortunate fact of the matter is that a different set of equations should really be used for gasses, because they're compressible, but it's late at night and I don't feel like dragging out my fluid mechanics books.

In this case, the force caused by energy losses created by velocity head would overwhelm conventional frictional forces, so you'd end up with a fairly accurate model of how the raindrop would fall, assuming that you could figure out the area of the raindrop being applied to the force of pressure. The ideal would likely be to make the area of the raindrop a function of the forces acting upon it and the surface tension of water.