Question

What is the electric force between a glass ball with 3.5 µc of charge and a rubber ball with -4.5 µc of charge when they are separated by 5 cm?

Answer 1

they attract each other with force 
F=q1*q2/(4πεr^2), where 
q1=2.4 µC, q2=4.2 µC, 
r=4.9·10-2 m, ε=8.854·10^(-12) SI units. 
♦ F=2.4·10-6 * 4.2·10-6 /(4*pi* 8.854·10^(-12) *0.049^2)= 
=37.73 N;