일반물리학 2 — Coulomb's Law: Problem 2

2 In Fig. 21-11, four particles form a square. The charges are $q_1 = q_4 = Q$ and $q_2 = q_3 = q$. (a) What is $Q/q$ if the net electrostatic force on particles 2 and 3 is zero? (b) Is there any value of $q$ that makes the net electrostatic force on each of the four particles zero? Explain.