In my AP physics class we were recently discussing the drag force and how it applies to Newton's second law [please no comments on the validity of Newton's law or inertial reference frames! :) ].
In any case, an example I pulled from Sears, Zemansky, and Young had a resistive force proportional to mv. The Drag force given by Halliday and Resnick, however, does not depend on the mass of the object in question at all. My question is: is the resistive force in the Sears et al. problem an accurate picture of reality or simply made up to simplify the math? It doesn't seem reasonable to me that the resistive force would depend on the mass...otherwise no one would think that heavy objects fall faster!