Speed at the bottom of the track

[bcd201115]

Homework Statement

A child slides down a curved playground slide that is one quadrant of a circle of radius R. If he starts from rest and there is no friction, find his speed at the bottom of the track. (the motion of this child is exactly the same as that of a child on a swing of length R, with the other end held at point 0)

Homework Equations

I can't figure this one out, really could use some help. Anyone know how to get me started at least?

The Attempt at a Solution

 

[JesseC]

Conservation of energy.