Solve Freefall Problem: Find Speed of Stone Thrown Upward

[culexor]

I need help getting the base equations for a situation like this so I can complete all of the other problems on the page. Thanks ahead of time.

Homework Statement

A stone is thrown straight upward and it rises to a height of 20.0m. With what speed was it thrown?

Homework Equations

This is what I need.

The Attempt at a Solution

Answer: 19.8 m/s (given, the equations are what I need)

 

[rock.freak667]

g is constant so the kinematic equations apply

those are v=u+at;s=ut+1/2at^2;v^2=u^2+2as

Where v=final speed,u=initial speed,a=acceleration,s=displacement

 

[Shooting Star]

It's always very useful and time saving to use the symmetry in the rise and fall of an object. This means that in this case we have to calculate the speed after a fall of 20 m from rest. The eqn v^2 = 2gh gives it directly.