# Homework Help: Physics Electric Field Problem

1. Feb 17, 2013

### asheik234

1. The problem statement, all variables and given/known data
k = 9 * 10^9

Sphere A of mass m = 0.0004 kg holds a positive charge qA = 3.0 10^-5 C and is fixed in place. Point P is d = 0.03 meters away from Sphere A.

Sphere B is identical in mass to sphere A, but carries a charge of qB = 3.6 10^-5 C. Sphere B is brought from a distant location and fixed at point P.

If both spheres are released from rest at the same time, how fast do the spheres move when they are very far apart?

2. Relevant equations
KE = (1/2)mv^2
KE = qV

3. The attempt at a solution

I keep getting different speeds for each ball using the first equation, any help would be appreciated.

2. Feb 17, 2013

### haruspex

Pls post your working, as per forum rules.

3. Feb 17, 2013

### asheik234

I'm not sure if I have to get the velocity of ball a or ball b, or get them both and average, I just need help on this part of the problem.

4. Feb 18, 2013

### asheik234

I'm not sure if I have to get the velocity of ball a or ball b, or get them both and average, I just need help on this part of the problem.

5. Feb 18, 2013

### haruspex

They're the same mass. What does conservation of momentum tell you about the relationship between their velocities?