A(-9x10^-9 C) 20mm B(5x10^-9 C) (a)calculate the force between the charges

(b)if A comes in contact with B Calculate the new charge on A and B

To calculate the force between two charges, you can use Coulomb's Law, which states that the force between two charges is directly proportional to the magnitude of the charges and inversely proportional to the square of the distance between them.

(a) Calculating the force between the charges:

1. Determine the magnitude of the charges:
Charge of A = -9x10^-9 C
Charge of B = 5x10^-9 C

2. Determine the distance between the charges:
Distance between A and B = 20 mm = 20x10^-3 m

3. Calculate the force using Coulomb's Law:
F = k * (|q1| * |q2|) / r^2

Where:
F is the force between the charges
k is Coulomb's constant, approximately 9x10^9 N m^2 C^-2
q1 and q2 are the charges
r is the distance between the charges

Plugging in the values:
F = (9x10^9 N m^2 C^-2) * (|-9x10^-9 C| * |5x10^-9 C|) / (20x10^-3 m)^2

Calculate:
F = (9x10^9 N m^2 C^-2) * (9x10^-9 C * 5x10^-9 C) / (20x10^-3 m)^2

F = (9x10^9 N m^2 C^-2) * (45x10^-18 C^2) / (400x10^-6 m^2)

F = (9x10^9 N m^2 C^-2) * (45x10^-18 C^2) / (400x10^-6 m^2)

F = (9x45) * (10^9 * 10^-18) / (10^6 * 400)

F = 405 * (10^(-9 - 18 + 6)) / 400

F = 405 * 10^-21 / 400

F = 405 / 400 * 10^-21

F = 1.0125 * 10^-21 N

Therefore, the force between the charges A and B is approximately 1.0125 * 10^-21 Newtons.

(b) If A comes in contact with B, and assuming no charge is lost during the contact (conservation of charge), the new charge on A and B will be equal.

Total charge before contact = Charge of A + Charge of B
Total charge before contact = (-9x10^-9 C) + (5x10^-9 C) = -4x10^-9 C

Since the charges are equal after contact, the new charge on A and B will be (-4x10^-9 C) / 2 = -2x10^-9 C.

Therefore, after contact, the new charge on both A and B will be -2x10^-9 Coulombs.