1. The problem statement, all variables and given/known data Ball A is dropped from the top of a building. One second later, ball B is dropped from the same building. As time progresses, the distance between them A) increases. [<-- Correct Answer] B) remains constant. C) decreases. D) cannot be determined from the information given. 2. Relevant equations N/A 3. The attempt at a solution Keep in mind that the solution key could and is often wrong. I would say it is D) Cannot be determined from the information given Because we do not know the surface area of each of the Balls, Ball A & Ball B, thus we cannot determine air resistance, which affects the balls. We do not know the initial velocity. It just says the ball is dropped from the top of a building. This does not provide the information about the velocity, which is critical in that. [itex]F_D = 0.5pv^2(C_D)(A)[/itex] where this is the drag equation. http://en.wikipedia.org/wiki/Drag_equation So we do not know the density of the fluid (air), we do not know the speed of the object either. Thus, we cant determine air resistance, which is important in the problem. What other reasons can you possibly think of that could prove the answer is (D)? Thanks!