How Long Does It Take for Two Rocks Thrown from a Bridge to Hit the Water?

[mcryder16]

Homework Statement

Heather and Jerry are standing on a bridge 46 m above a river. Heather throws a rock straight down with a speed of 30 m/s. Jerry, at exactly the same instant of time, throws a rock straight up with the same speed. Ignore air resistance. How much time elapses between the first splash and the second splash?

Homework Equations

Need help finding the equation?

The Attempt at a Solution

 

[nickjer]

Solve for the time it takes both rocks to hit the water under a constant gravitational acceleration. You know initial velocity, displacement, and acceleration. All that you need is time. So find the best kinematic equation for your problem.