Can you solve these physics riddles? ft Simone Giertz - Part 1/3

The heavier ball will experience more air resistance, once your reach terminal velocity.  At the same speeds both balls will experience the same amount of air resistance, however, the force of air resistance will have a greater effect on the lighter ball since the ratio of air resistance to momentum is larger.  The lighter ball will reach its terminal velocity at a slower speed.  The heavier ball, meanwhile, will continue to speed up and with the higher velocity you get more air resistance.
This is pretty evident when you look at the formula for calculating Terminal Velocity and see that mass is a factor in the calc.