Calculating trajectory of ball rolling down slope and off launch ramp
rubinho, if all the balls are falling in EXACTLY the same spot, you've made a mistake, the inertia of the heavier ball should carry it farther horizontally, even if it does fall vertically at the same rate. (Gallileo did prove that!)
the proof that this is true can be found in the way the manhattan project used to separate U238 from U235. using a cyclotron, they accellerated raw uranium atoms and then used magnetic fields to deflect them. the heavier atoms (U238) were deflected less and went to one recieving bucket, and the lighter U235 went to another. this was before they worked out gas centrifuge technology which was orders of magnitude more efficient. (hint hint....)
All that being said, it is possible that the mass difference may not be big enough to make your design work as originally concieved.
also do not discount air resistance and ballistic efficiency. this will actually help as the lighter balls will loose a larger percentage of their energy to air resistance than the heavy ones will. this is why there is such a thing as terminal velocity.