# Homework Help: Free Fall Question

1. Sep 8, 2008

### azn4lyf89

A ball is thrown upward with speed V. At the instant the ball is thrown, second ball is dropped from rest at a height H above the thrown ball, but not directly above it. Ignore air resistance. How much time elapses before the balls pass each other? Find a value of H such that the ball thrown upward is at its highest point when the dropped ball passes.
For the first question, do I need to come up with an equation for both balls and set them equal to each other to find the time when they pass each other? It seems as if I would have two unknowns when I do this. And for the second question do I need to set the velocity equal to 0 to find when the ball reaches its highest point?

2. Sep 8, 2008

### mezarashi

For the 1st question, review the kinematics equations again. There is an equation where displacement is expressed as a function of: initial velocity, gravity, and time. By equating this displacement, you can then solve for the time.

For the 2nd question, you are right on!