(a) Imagine that Charlotte drops a ball from a window on the twentieth floor of a building while at the same time Fred drops another ball from a window on the nineteenth floor of that building. As the balls fall, what happens to the distance between them (assuming no air resistance)?
(b) Next imagine that Charlotte and Fred are at the same window on the twentieth floor and that Fred drops his ball a few seconds after Charlotte drops hers. As the
balls fall, what happens to the distance between them now (again assuming no air resistance)?