posted by Nuwaya .
A particle carring a charge of 6*10^-5C is located half way b/n two charges 40cm apart. One carries a charge of 1*10^-4C and the other -1*10^-4 C. If the three charges lie on the same straight line, what is the magnitude and direction of force on the 6*10^-5 C charge?
Add the Coulomb forces. They will be equal and in the same direction, because the 6*10^-5 C charge is midway between charges of equal magnitude and opposite sign.