Electrical Potential Difference between two plates

[coolgirl]

Homework Statement

HELP!
A charged particle is stationary between two horizontal charged plates. The plates are 2.0 cm apart. The particle has a mass of 4.0X10^-13 kg and a charge of 2.4 X 10^-18 C. Find the potential difference between the plates.

Homework Equations

V= EPE/q ?
...except I have no idea how to find the potential energy. Also, I have no clue how the mass given in the problem fits into an equation.

The Attempt at a Solution

I need someone to help me start this!

 

[Delphi51]

Looks like a force-balance problem. The force of gravity (down) on the particle is balanced by an equal electric force (up). Begin with Fg = Fe and fill in the detailed formulas before solving for what you want.

 

[coolgirl]

So is this how I would do it?:
PE=mgh
PE=(4.0x10^-13)(9.8m/s/s)(1.0cm)
PE=3.92x10^-12

V= EPE/q
V=3.92x10^-12/2.4x10_18C
V= 6.8x10^23V
I don't think I did it right...

 

[Delphi51]

Fg = Fe
mg = qE

 

[coolgirl]

Thank you :]