Answer
Organelles are separated based off of their densities in equilibrium centrifugation, while in velocity centrifugation organelles are separated off of their size.
Work Step by Step
Since equilibrium centrifugation separates particles based off of their densities, both large and small particles can come along if their densities are the same. Velocity centrifugation, on the other hand, exclusively separates organelles of the same size.
