Answer
$F=8.99$ $KN$
Work Step by Step
From Coulomb's law
$F=\frac{q_1q_2}{4\pi{\epsilon_{\circ}}r^2}$
but for point charges $q_1=q_2$
hence
$F=\frac{q.q}{4\pi{\epsilon_{\circ}}r^2}$
$F=\frac{q^2}{4\pi{\epsilon_{\circ}}r^2}$
given that $r=1Km=1000m$
Putting the values, we get
$F=\frac{(1.00)^2}{4(3.14)(8.854\times10^{-12})(1000)^2}$
$F=8.99\times10^3 N$
or
$F=8.99$ $KN$
