1. The problem statement, all variables and given/known data
a charge of q is fixed on a plane at the origin of an xy coordinate system and a charge 3q is fixed at (3cm, -3cm). where must a charge of -2q be placed at rest for it to be in equilibrium so that it remains at rest? is the equilibrium stable?
2. Relevant equations
coulomb's law
3. The attempt at a solution
tiny-tim
Sep1-08, 07:32 AM
a charge of q is fixed on a plane at the origin of an xy coordinate system and a charge 3q is fixed at (3cm, -3cm). where must a charge of -2q be placed at rest for it to be in equilibrium so that it remains at rest? is the equilibrium stable?
Hi briteliner! Welcome to PF! :smile:
How far have you got?
Can you work out what line it must be on, and whether it's between or outside the charges? :smile:
briteliner
Sep1-08, 03:43 PM
i don't really know where to start, all i know is that since the -2q charge is negative it should be in between the charges. i think?
tiny-tim
Sep1-08, 04:41 PM
i don't really know where to start, all i know is that since the -2q charge is negative it should be in between the charges. i think?
Hi briteliner! :smile:
Yes, it is repelled by both the other charges, and so it must be between them.
ok … there's a line joining the two other charges … which side of that line must the third charge be on? :smile:
briteliner
Sep1-08, 04:47 PM
why would it make a difference which side it is on?