# Find the time at which the two balls collide

A ball is thrown straight up from the ground with speed Vo . At the same instant, a second ball is dropped from rest from a height H , directly above the point where the first ball was thrown upward. There is no air resistance.

1-Find the time at which the two balls collide.
Express your answer in terms of the variables "Vo","H" , and appropriate constants..

2-Find the value of "H" in terms of "Vo" and "g" so that at the instant when the balls collide, the first ball is at the highest point of its motion.
Express your answer in terms of the variables "Vo" and "g" .

## Answers and Replies

LowlyPion
Homework Helper
Welcome to PF.

How would you think to start?