Finding Neutral Points in a Charged System

[jimbo71]

Homework Statement

A long line carrying a uniform linear charge density + 50.0*10^-6C/m runs parallel to and 10.0 cm from the surface of a large, flat plastic sheet that has a uniform surface charge density of - 100*10^-6C/m^2

Find the location of all points where an alpha particle would feel no force due to this arrangement of charged objects.
L= ? m from the line

Are they above the line or between the line and the sheet?

Homework Equations

The Attempt at a Solution

I have no idea where to start. please help

 

[Hannisch]

Do you know anything about electric force? And how charge density is related to the total charge?

Basically, what have you covered concerning electricity so far?

 

[jimbo71]

electric flux for uniform electric field and nonuniform electric field. we are begging to discuss gauss's law and guassian surfaces

 

[jimbo71]

i need help??!?