Đáp án: *đổi: q1=16uC=16.10^-6C; q2=-64uC=-64.10^-6C; q0=4uC=4.10^-6C
**a)r1=AM=60cm=0,6m; r2=BM=40cm=0,4m *F = F10+F20 *F10 = k.|q1.q0|/r1^2 = 9.10^9.(16.10^-6).(4.10^-6)/0,6^2 = 1,6N *F20 = k.|q2.q0|/r2^2 = 9.10^9.(64.10^-6).(4.10^-6)/0,4^2=14,4N *>> F=1,6+14,4=16N