Hi, I tried using pendulum formula's, but it yields contradictions. The best way I can think of to explain it, is to imagine this..

2 pieces of string hang from the ceiling, and attach it to a ruler (so the places where the string holds the ruler up, are the same distance from the center of the ruler. Now add to masses to both ends of the ruler.

Its been a long time since ive done mechanics, and cant really find the maths to explain it.

Thanks.