Simple Pendulum Centripetal Acceleration

[robwashere]

Homework Statement

http://screensnapr.com/v/tC6gC3.jpg

Homework Equations

Im guessing: Centripetal Acceleration = v^2/r
PE = mgh
KE = .5mv^2

The Attempt at a Solution

I tried to convert the givens into velocity by using .5mv^2, but that does not work.

 

[Doc Al]

Hint: Apply Newton's 2nd law.

 

[robwashere]

Hint: Apply Newton's 2nd law.

You sir, are a genius! Thanks!