Question

(a) Two point charges totaling 8.50 µC exert a repulsive force of 0.250 N on one another when separated by 0.520 m. What is the charge on each?

smallest charge 7.5E-6 Incorrect: Your answer is incorrect. µC largest charge 1.0E-6 Incorrect: Your answer is incorrect. µC (b) What is the charge on each if the force is attractive? smallest charge 7.5E-6 Incorrect: Your answer is incorrect. µC largest charge -1.0E-6 Incorrect: Your answer is incorrect. µC

Answer 1

a) force is repulsive then both are of same type charge.

q1 + q2 = 8.50 uC

q1 = (8.50 - q2) uC

Fe = kq1q2 / d^2

0.250 = 9 x 10^9 x (8.50 -q2)q2 x 10^-12 / 0.520^2

(8.50 -q2)q2 = 7.51

q2^2 - 8.50q2 + 7.51 = 0

q2 = 1   and 7.50

smallest charge = 1 uC

largest charge = 7.50 uC

b) force is attarctive then one is negative then other is positive.

q1 is +ve and q2 is -ve then

q1 - q2 = 8.50

q1   = 8..50 + q2

Fe = kq1q2 / d^2

0.250 = 9 x 10^9 x (8.50 + q2)q2 x 10^-12 / 0.520^2

(8.50 -q2)q2 = 7.51

q2^2 + 8.50q2 - 7.51 = 0

q2 = 0.806 and -9.31

so smallest charge = 0.806 uC

largest charge = 9.31 uC

1 have to be +ve and other have to be -ve.

you can consider any of these -ve or +ve/