Question

Two charged spheres exert a force of 5.54 × 10^-4 N on each other. If one of the spheres has a charge of 3.72 × 10^-9 C and the other sphere has a charge of 4.32 × 10^-6 C, how far apart are the charged spheres?

Answer 1

$F=\frac{kq_1q_2}{r^2}\implies$

$r=\sqrt{\frac{kq_1q_2}{F}},$

$r=\sqrt{\frac{9\cdot 10^9\cdot 3.72\cdot 10^{-9}\cdot 4.32\cdot 10^{-6}}{5.54\cdot 10^{-4}}}=51~cm.$