A charge of 3.0 nC and a charge of 5.8 nC are separated by 53.40 cm. Find the equilibrium position for a -4.7 nC charge.

Answer 1

Since q1 and q2 are positive charges, q3 in its equilibrium position has to be between them at the distance “x” from the charge q1.
F1=F2.
Use Coulomb’s Law
F1= k•q1•q3/x²,
F2 = k •q2•q3/(r-x)²,
k•q1•q3/x²= k •q2•q3/(r-x)²,
q1 /x²= q2 /(r-x)².
Solve for “x”