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## Homework Statement

A charge 2Q is placed a distance 'd' from charge 4Q. A third charge 'q' is placed 3m from charge 2Q directly on the line between charges 2Q and 4Q. Find d and q such that the force between charges 2Q and 4Q is equal to 0.

## Homework Equations

Coulomb's law: f = k(|q1q2|)/r

^{2}

k = 8.99 x 10^9 (Nm^2/c^

^{2})

## The Attempt at a Solution

(k)(2Q)(q)/3 = [k(4Q)(q)]/(d - 3)

(d - 3)/3 = 2

d - 3 = 6;

d = 9m?

k(2Q)(q)/3 + [k(4Q)(q)]/6 = k(2Q)(4Q)/9;

q[(k4Q)/6 + (k4Q)/6] = k8Q

^{2}/9;

q[k4Q/3] = k8Q

^{2}/9;

q = (3)(2Q)/9 ?

q = 2Q/3 ?