Question

at what separation should two equal charges one coulomb each be placed so that the force between them equal the weight of a 50 kg person

Answer 1

Weight of a 50kg person=500N (taking g=10m/s^2)
By Coulomb's inverse square law,
F=$\frac{Kq_{1} q_{2}}{ r^{2} }$=K/r^2 (Because q1=q2=1C)
500=K/r^2
500=9 x $10^{9}$/r^2
r^2=18 x $10^{6}$
r=4.24264 x $10^{3}$ meters
r = 4.24 km