Question

A point charge (Q1) has a magnitude of -7 uC. A second charge (Q2) has a magnitude of -5.5 uC and is located 143 cm from the first charge. Find the magnitude of the force between the two charges.

Answer 1

Given:

$q_1=-7.0*10^{-6}\:\rm C$

$q_2=-5.5*10^{-6}\:\rm C$

$r=1.43\:\rm m$

The Coulomb's law says

$$F=k\frac{|q_1||q_2|}{r^2}$$ $$F=9*10^9*\frac{7.0*10^{-6}*5.5*10^{-6}}{1.43^2}=0.17 \:\rm N$$