Coulomb's Law, finding acceleration direction

[loukiz]

Homework Statement

Two charges q1 = -7 and q2 = -2, both charges are fixed in place and the distance between them is 2m. Third negative charge q3 is moving along the vertical line that connects two charges.

1) net force acting on q3 = 0; where is the charge located ?
2) If charge q3 is released 0.5m above charge q1, in which direction is it going to accelerate ?

Homework Equations

F1 - F2 = 0
x = position of q3
q₁/x² = q₂/(d-x)²

The Attempt at a Solution

After solving #1 the final formula that i came up with is x = d√q₁/q₂ / 1 + √q₁/q₂

and #2 i have no clue how to solve this one...

 

[Bystander]

released 0.5m above charge q1,

Where is q₂ relative to q₁? Above? Below?

 

[loukiz]

Where is q₂ relative to q₁? Above? Below?

q2 is above q1

 

[Bystander]

Net force on q₃ from the two fixed charges is then what?