Calculating Mass Using Electric Field and Force Equations

[krony23]

Homework Statement

In a laboratory, a particle of charge -6C is held stationary because it is placed in an electric field E=(0,0,-15)N/C which suspends it against gravity. What is the mass of the particle? Give answer in kg.

Homework Equations

I THINK
E= F/q
F= ma

The Attempt at a Solution

Ok, so I haven't actually had a chance to attempt this yet because A) I don't understand the notation of E in this equation, so I don't know if it is acceptable to just use -15 for E, and B) if I even have the right equations to use, I don't know what the acceleration is. Please help

 

[rock.freak667]

Homework Statement

In a laboratory, a particle of charge -6C is held stationary because it is placed in an electric field E=(0,0,-15)N/C which suspends it against gravity. What is the mass of the particle? Give answer in kg.

It suspends it against gravity, so what is the relationship between the electric force and the mass?

 

[krony23]

I don't really get what that means about it though.

 

[rock.freak667]

I don't really get what that means about it though.

The only forces acting on the mass are its weight and the electric force. If it is being suspended, what is the resultant force on it?