At what separation will two charges, each of magnitude 8 µC, exert a force of 1.4 N on each other? (mult cho.)

Question

At what separation will two charges, each of magnitude 8 µC, exert a force of 1.4 N on each other?
A) 5.1 * 10^-6 m
B) 0.41 m
C) 0.48 m
D) 2.0 m
E) 0.64 m

I am trying to finish my exam review, and don't know how to do this. Best answer will be awarded points.

Answer 1

F=k*q1*q2/r^2
k=1/(4*pi*eo)=8.988×10^9 N m2

1.4= 8.988×10^9 *8^10^-6*8^10^-6/r^2
r^2=0.41085
r=0.641m

E)0.64 m

Answer 2

From the Coulomb's Law: Kq1q2/r^2 = F, we have

(9x10^9)(8x10^-6)^2/r^2 = 1.4

Solving for r gives, r = .64 m

Answer 3

it somewhat is Coulomb legislations. F = ok*q1*q2/r^2 r = sqrt(ok*q1*q2/F) = sqrt ( 9 * 10^9 * 2.5 * 2.5 * 10^-12 / 6.0 * 10^-4 ) = sqrt(9.375 * 10) = 9.7 m to entice each distinctive the fees could be opposite, in the different case they repulse.

Answer 4

F = kq1q2/r^2

So, 1.4 = 9x10^9 * 8x10^-6 * 8x10^-6 / r^2

r = sqrt ( 9x10^9 * 8x10^-6 * 8x10^-6 / 1.4)

r = (don't have a calculator on me)