Question

At what separation should two equal charges, $1.0C$ each, be placed so that the force between them equals the weight of a $50kg$ person ?

Answer 1

$\text{Step 1: Force due to weight}$

$F=mg=50kg\times 10m{s}^{-2}=500N$

$\text{Step 2: Force between the Charges}$

From Coulomb's law:

$F=\frac{K{q}_1{q}_2}{r^2}$

$\Rightarrow 500N=\frac{9\times {10}^9\times 1C\times 1C}{r^2}$

$\Rightarrow r^2=\frac{9\times {10}^9}{500}$

$\Rightarrow r=4.24\times {10}^{3}m$