Coulomb's law for the magnitude of the force F between two particles with charges Q and Q' separated by a distance, d is |F| =K *|QQ'|/d^2
where K = 1/4 peo = 8.854*10^-12
nC is the permittivity of free space.
Consider two point charges located on the x axis: one charge, q1 = -19.5nC , is located at x1 = -1.680 m ; the second charge, q2 = 31.5 nC, is at the origin (x = 0.0000). What is the net force exerted by these two charges on a third charge q3 = 52.5 nC placed between q3 and at x3= -1.245 m ? Your answer may be positive or negative, depending on the direction of the force.