Conservation of energy I think

[Benevelli]

Homework Statement

PLEASE HELP: A bead at the end of a vertical spring moves without friction along a horizontal wire. WHen the spring is perfectly vertical , the spring is neither stretched or compressed. Show that the bead experiences a restoring force, and that if x is small, then the magnitude of the force is proportional to x^3 rather x^1. You will want to use the approximation (1+x)^n = 1+nx for x<<1

Homework Equations

U + K = E

The Attempt at a Solution

I tried thinking about this like a pendulum with kx as the restoring force. Other than that, my work has gotten me nowhere.

 

[haruspex]

Draw a free body diagram for the bead at some displacement x. What are the forces on it?