Two Objects, Constant Acceleration, 1D Forces, Collision Question

[Hotsuma]

Homework Statement

A ball is dropped from the top of a 50.0 rm m-high cliff. At the same time, a carefully aimed stone is thrown straight up from the bottom of the cliff with a speed of 21.0 m/s. The stone and ball collide part way up.

Homework Equations

v = v₀+at
x = x₀ + v₀t + (1/2)at²
v² = v²₀+2a(x- x₀)

The Attempt at a Solution

Two objects, each with different components of one-dimensional motion. The two objects will share a common impact time because they are put into motion at the same time. I have tried solving for time and setting the equations equal to each other, but this yields no result because when I arrange the quadratic formula it evaluates to y = 0, which doesn't make sense. I don't need explicit help (although I don't mind, I just hate typing this out so I don't expect people trying to help me to), I just need a direction to take this problem.

Thanks

 

[LowlyPion]

What is the question?

 

[LowlyPion]

If they collide there are two things that must be equal.

Time. and Height.