# Homework Help: Balls collision

1. May 10, 2005

### kidia

Does anyone can help me on this please?
Ball A is dropped from the top of building at the same instant the ball B is thrown vertically upward from the ground.When the balls collide,they are moving in the same direction,and the speed of A is 4 times that of B.At what fraction of the height of the building does collision occurs?
I will appreciate.

2. May 10, 2005

### Hyperreality

Think of ways to express the paths of both balls. Maybe a kinematic equation could help or perhaps the useful K.E. equation.... $$K.E. = \frac{1}{2}mv^2$$