Calculating Potential Difference in Suspended Capacitor

[jesuslovesu]

Homework Statement

A small object of mass m carries charge q and is suspended by a thread between the vertical plates of a capacitor. The plate separation is d. If the thread makes an angle $$\theta$$ with the vertical, what is the potential difference between the plates.

Homework Equations

$$\Delta V=-Ed$$
$$C\Delta V=q$$
E = kq/r^2
C = e0*A/d

The Attempt at a Solution

I drew a free body diagram, but since the length of the thread isn't given, it doesn't appear to help.
I'm having a hard time finding a relationship between theta, m, d, and q. Any hints?

 

[berkeman]

What is the relationship between the voltage on the plates and the electric field between them? What is the equation for the force on the charged mass due to the electric field? What is the force of gravity on the mass?

 

[jesuslovesu]

Got it now, thanks