Question

Find the electrostatic force between charges of +2.0 C and +5.0 C separated by a distance of 75m in a vacuum.

Answer 1

Given:

$q_1=\rm 2.0\:C$

$q_2=\rm 5.0\:C$

$r=\rm 75\:\rm m$

The Coulomd law says

$$F=k\frac{q_1q_2}{r^2}$$

Hence

$$F=9*10^9*\frac{2.0*5.0}{75^2}=1.6*10^7\:\rm N$$