1. The problem statement, all variables and given/known data Ball A is dropped from the top of a building of height 'h' at the same instant that Ball B is thrown vertically upward from the ground. When the balls collide, they are moving in opposite directions, and the speed of A is twice the speed of B. At what height does the collision occur? 2. Relevant equations x1=x0 + Vot - 1/2gt^2 I've been having a hard time with this. I just cant get it.