## College Physics (4th Edition)

(a) The magnitude of the electric force acting on the +2.0-nC point charge is $6.0\times 10^{-5}~N$. Since a positive charge and a negative charge attract each other, this force is directed toward the -3.0-nC point charge. (b) The magnitude of the electric force acting on the -3.0-nC point charge is $6.0\times 10^{-5}~N$. Since a positive charge and a negative charge attract each other, this force is directed toward the +2.0-nC point charge.
(a) We can find the electric force exerted on each point charge: $F = \frac{k~q_1~q_2}{r^2}$ $F = \frac{(9.0\times 10^9~N~m^2/C^2)~(2.0\times 10^{-9}~C)(-3.0\times 10^{-9}~C)}{(0.030~m)^2}$ $F = -6.0\times 10^{-5}~N$ The magnitude of the electric force acting on the +2.0-nC point charge is $6.0\times 10^{-5}~N$. Since a positive charge and a negative charge attract each other, this force is directed toward the -3.0-nC point charge. (b) The magnitude of the electric force acting on the -3.0-nC point charge is $6.0\times 10^{-5}~N$. Since a positive charge and a negative charge attract each other, this force is directed toward the +2.0-nC point charge.