Question:
Two basketballs are dropped from a high building through the air. One ball is hollow and the other filled with rocks. Which accelerates more? Defend your answer.

My answer:
Although the basketball with rocks in it has more mass than the hollow basketball, they both have the same acceleration. Both basketballs have 10 times as much force as their weight acting on 10 times as much mass, causing them to have the same acceleration.

I got this answer by my book, which says that a falling 10-kg boulder "feels" 10 times the force of gravity (weight) as a 1-kg stone. (Newton's second law tells us to consider mass). The books says: Can you see that ten times as much force acting on ten times as much mass produces the same acceleration as the smaller force acting on the smaller mass?

x_x Did I do this correctly? Thank you! Please do not give away the answer if I did it incorrectly :]

You would be correct if you ignore air resistance. The effect of air resistance is to slow the ball by an amount proportional to the ball's area times the velocity squared. Can you see how air resistance might change your answer?