[tex]Dane:\\q_1 = 1 \ nC = 10^{-9} \ C\\q_2 = -1 \ nC = -10^{-9} \ C\\r = 10 \ m\\k = 9\cdot10^{9}\frac{Nm^{2}}{C^{2}}\\Szukane:\\F = ?[/tex]
Z prawa Coulomba:
[tex]F = k\cdot\frac{|q_1\cdot q_2|}{r^{2}}\\\\F = 9\cdot10^{9}\frac{Nm^{2}}{C^{2}}\cdot\frac{|10^{-9} \ C\cdot(-10)\cdot10^{-9} \ C|}{(10 \ m)^{2}}\\\\F = 9\cdot10^{9}\cdot\frac{10^{-18}}{10^{2}} \ N\\\\\boxed{F = 9\cdot10^{-11} \ N}[/tex]
