# Kinematics equations with collision fo 2 balls

1. Oct 1, 2008

### mjolnir80

1. The problem statement, all variables and given/known data
a ball is shot straight up from the ground with speed Vo. simultaneously, a second rubber ball at height h directly above the first ball is dropped from rest
at what height above the ground do the balls collide?asnwer should be a symbolic expression in terms of Vo and g.

2. Relevant equations
kinematics equations

3. The attempt at a solution
we can use (delta)x = Vot + 1/2 a t2 and since we know that the final positions are equal we can write this equation for the 2 balls and make them equal to each other
but the equation of the second ball would have a x(initial) for the ball in the equation (assuming the base line is the ground).........

can someone help me out please. Thanks in advanced

2. Oct 1, 2008

### LowlyPion

You mostly have it.
Construct the upward equation first:
X=Vo*t - 1/2*g*t2

Then construct the equation from rest:
X= h - 1/2*g*t2

If you solve for t then you just substitute into one of the x equations for the height.