# Homework Help: Electric Potential of 2 positive charges, and the speed

1. Sep 14, 2010

### GenericPhy

QUESTION 1
1. The problem statement, all variables and given/known data

Two positive charges, each with Q = +10 µC, are fixed to the x-axis at x = +a and x = -a, where a = 4 m.

(a) Find the electric potential at point A on the y-axis where (xA, yA) = (0, b) and b = 5 m. Take the zero of potential to be at infinity.

(b) A particle with charge q = -4 µC and mass m = 2.2 x 10-4 kg is released from rest at point A. Find its speed at the origin.

2. Relevant equations

Gauss's Law?

3. The attempt at a solution

I know I need to use superposition to calculate the potential at point A due the left-hand charge and add it to the potential at A due to the right-hand charge...

Last edited: Sep 14, 2010
2. Sep 14, 2010

### collinsmark

Hello GenericPhy,
Welcome to Physics Forums!
Gauss' law alone won't give you the solution to this problem. You need to look up the definition of electric potential. More-so, I'm betting that your textbook/coursework already has the equation for the electric potential of point charges already worked out for you.
Superposition. Yes, that is part of the correct approach. After you arrive at the correct equation for electrical potential, show us what you can do with it!