Question

The diagram shows two positively charged spheres, one with three times the charge of the other. The spheres are 16 cm apart, and the force between them is 0.28 N. What are the charges on the more charged sphere?
(Hint use coulombs law where K= 8.9×109 kg⋅m3⋅s−2⋅C−2.)

Answer 1

$$F=k\frac{Qq}{r^2}=k\frac{Q^2}{3r^2}\\0.28=9\cdot10^9\frac{Q^2}{3(0.16)^2}\\$$

$$Q=1.55\cdot10^{-6}C$$