Question

(a) Two point charges totaling 7.00

Answer 1

q1q2 = Fr^2/K

q1q2 = 0.3 * 0.441*0.441/(9e9)

q1q2 = 6.48 *10^-12

use thw identity (q1-q2)^2 = (q1+q2)^2 -4q1q2

(q1-q2)^2 = 7e-6*7e-6 -(4*6.48 e-12)

q1-q2)^2 = 23.08 *10^-12

(q1-q2) = 4.8 uC

as (q1+q2) = 7 uC

adding them

2q1 = 11.804

q1 = 5.9 uC   or 6 uC (largest charge)

q2 = 7-5.9 = 1.1 uC   or 1uC ( smallest charge)

b.

when force is attractive,

(q1-q2)^2 =   7e-6*7e-6 -(4*-6.48 e-12)

q1-q2 = sqrt(74.92 e-12)

q1 -q2 = 8.655 uC

q1+q2 = 7uC

adding them

2q1 = 15.655

q1 = 7.82 uC ( largest charge)

q2 = 0.82 uC (smallest charge)