Find the natural frequency of a system of two pendulums

[joker_900]

Homework Statement

OK I haven't been given a definite question with values, but how would you find the natural frequency of a system of two pendulums coupled by a spring?

Homework Equations

a= -gx/l
T=2pi sqrt(l/g)

The Attempt at a Solution

Well the thing is, I know I need to consider each pendulum/spring separately and get two equations of motion, but I'm not sure how. All i know about pendulums are those two equations above. When I've had similar problems with springs I've been able to find the resultant force as a function of x and go from there. But in this case I just came up with the resultant -mgx/l - lamda(x-0.5l) = ma

Help!

 

[physics girl phd]

I know I need to consider each pendulum/spring separately and get two equations of motion, but I'm not sure how.

Some thoughts:
Have you drawn out a picture of the system? Are the pedulums fixed at the same point at the top or are their top points separated by the natural length of the spring?

Then: Can you use free body diagrams to find out the forces on the bobs of the pendulums? What if you displace one bob in the system by a small angle?