Question

Two equal charges ar eplaced at a separation of 1.0 m. What should be the magnitude of the charges so that the force between them equals the weight of a 50 kg person?

Answer 1

Let each charge = qC, AB = 1m
wt. of 50 kg person
$=50\times g=50\times 9.8=490$ N
$F=9\times {10}^9\times \frac{q^2}{r^2}=490N\Rightarrow q^2=(54.4\times {10}^{-9})\Rightarrow q=\sqrt{54.4\times {10}^{-9}}={10}^{-5}\times 23.323=23.323\times {10}^{-5}=2.3\times {10}^{-4}C$