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A charge +Q is located at the origin and a second charge, +4Q is at a distance d on the x-axis. where should a third charge, q, be placed, and what should be its sign and magnitude, so that all three charges will be in equilibrium.

I'm pretty sure the answer is charge of -3Q and distance of d/3. Can someone just confirm if this is right?

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What do you mean by equilibrium here? I don't think if you place the three charges as you suggest they will all have no net force acting on them. – Alexander Jan 27 '12 at 20:54
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Hi user1174275, and welcome to Physics Stack Exchange! This is a site for conceptual questions about physics. As dmckee said, this prohibits "do-my-homework" type questions, but it also means that questions which are just asking for someone to check your work are inappropriate. If you have a particular reason to believe that your method is wrong, you can edit the question to be about that, and it will make a great improvement. – David Zaslavsky♦ Jan 27 '12 at 21:17

closed as too localized by Qmechanic♦, David Zaslavsky♦ Jan 27 '12 at 21:15

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