Problem 16: If two point charges q1 and q2 at some distance r attract each other with a force of 60N, what force would they exert on each other if r is increased fivefold (×5), q1 is tripled (x3); and q2 is quartered (×1/4) and the signs of both charges are reversed. The two charges will (A) attract each other with a force of 1.8N. (B) repel each other with a force of 1.8N. (C) attract each other with a force of 2000N. (D) attract each other with a force of 9N. (E) repel each other with a force of 9N.

Problem 16: If two point charges q1 and q2 at some distance r attract each other with a force of 60N, what force would they exert on each other if r is increased fivefold (×5), q1 is tripled (x3); and q2 is quartered (×1/4) and the signs of both charges are reversed. The two charges will (A) attract each other with a force of 1.8N. (B) repel each other with a force of 1.8N. (C) attract each other with a force of 2000N. (D) attract each other with a force of 9N. (E) repel each other with a force of 9N.