Originally Posted by
Tinstaafl
Now add a fluid such as air. The only effect the fluid has is to provide a retarding force - 'drag' - reducing the acceleration of gravity. Drag is not affected by mass. Cd=1/2 rho v^2 s remember. So, as long as the objects *only differ in density* they will fall at the same rate.
It's true as far as it goes. Drag is not affected by mass, but the *force* of gravity certainly is; in fact it's proportional to mass.
And for objects of different masses, which are otherwise externally identical, the *force of gravity is higher for the object with greater mass, so the *force* of gravity will reach equilibrium with the *force* of drag, at a higher airspeed. And when the *force* of gravity reaches equilibrium with the *force* of drag, the object will no longer accelerate. And like I said that, occurs at a higher airspeed for the more dense object (assuming same volume) .