Question

A charge of 2.1 nC and a charge of 4.7 nC are separated by 57.90 cm. Find the equilibrium position for a -4.7 nC charge. _______________cm from the 2.1 nC charge.
i know you have to use coulomb's law but how can i use it

Answer 1

F1 =F2
k•q1•|q3|/x^2 = k•q2•|q3|/(d-x)^2

where d-x = (0.579 - x ) m

Answer 2

To be ever so much easier to find X for the algebraically challenged.

X= d*SQRT(K*q1*q3)/SQRT(K*q2*q3)+ SQRT(K*q1*q3)