A negative charge of -0.0005 C exerts an attractive force of 9.0 N on a second charge that is 10 m away. What is the magnitude of the second charge?
q1= -0.0005 C
q2= ?
F=9.0 N
D= 10m
K=9.0 x 10^9 N x m^2/C^2
F=Kq1q2
----------------
D^2
+36916 Coulomb's Law
F = kc q1 q2 / (r^2)
9 = (9 x109) (.0005) (q2) / ( 102) N
q2 = ( 9* 102) / [(9x109)(.0005)] C Since it is an ATTRACTIVE force q2 will be positive (since q1 is negative) You can finish ! 
