Question

1. The electric force between two point charges with a magnitude of 800uC and 900uC is 15 N. How far apart are the two charges in cm?

2. A force of 500 N between two identical point charges is separated by a distance of 47m. Calculate the magnitude of the two point charges.

Answer 1

1.

$$r=\sqrt{\frac{kq_1q_2}{F}}\\ =\sqrt{\frac{9*10^9*800*10^{-6}*900*10^{-6}}{15}}=21\:\rm m$$

2.

$$q=\sqrt{\frac{Fr^2}{k}}\\ =\sqrt{\frac{500*47^2}{9*10^9}}=0.011\:\rm C$$