Where is the location of zero net force between two fixed charges?

[NewtonRoxU]

Homework Statement

A positive point charge Q1 = 2.51×10-5C is fixed at the origin of a coordinate system. A second positive charge Q2 = 4.07×10-6C is fixed to the x-axis at x = +2.07m. Find the location of the place along the x axis, where the net-force on an arbirary test-charge (positive or negative) between these two charges is zero.

Homework Equations

Coulomb's Law

The Attempt at a Solution

My guess at this problem is to use Coulomb's equation to find where the force is equal to zero or to find the net force of the charges and somehow find where that equals zero. But I mostly need help on where to start with this problem.

 

[ehild]

Welcome to PF!

First show the relevant equations: What is the formula for the force between two point charges? Write it out, not only that it is Coulomb's Law...

Make a picture, showing the position of both charges Q1 and Q2, and draw the test charge somewhere between them, at position x. You need the forces exerted by Q1 and by Q2 on the test charge. What are they?
What should be x so as the net force on the test charge is zero?




ehild