Find postition on third charge question

[flaming]

Find postition of third charge question

Homework Statement

A charge of 1.57E-9 C is placed at the origin, and a charge of 4.23E-9 C is placed at x = 1.51 m. Find the position at which a third charge of 3.11E-9 C can be placed so that the net electrostatic force on it is zero.

Please help me out with this one

Homework Equations

The Attempt at a Solution

 

[quantumdude]

First question: Given that the charges are all positive, and that positive charges repel, do you think the 3rd charge should be placed to the left of both charges, to the right of both charges, or inbetween the two charges? Why?

 

[flaming]

First question: Given that the charges are all positive, and that positive charges repel, do you think the 3rd charge should be placed to the left of both charges, to the right of both charges, or inbetween the two charges? Why?

i guess it would be at the left of the two charges to counter them..i guess

 

[quantumdude]

Don't guess. Think.

If the 3rd charge were to the left of the other two, and the other two were both repelling it, then is it even possible that the net force on the 3rd charge is zero? Think about the directions of the forces on the 3rd charge.