Two charges, qA and qB, are separated by a distance, d, and exert a force, F, on each other.?

Question

a) What new force will exist if qA is doubled?
(b) What new force will exist if qA and qB are cut in half?
(c) What new force will exist if d is tripled?
(d) What new force will exist if d is cut in half?
(e) What new force will exist if qA is tripled and d is doubled?

Answer 1

Ok, let's call the first force : "F"

Now, remeber : F = K*qA*qB / d^2

a) F' = K*2qA*qB / d^2

F' = 2F, the force will be doubled.

b) F' = K*(qA/2)*(qB/2) / (d)^2 = K*qA*qB / 4d^2

F' = F / 4

c) F' = K*qA*qB / (3d)^2 = K*qA*qB / 9d^2

F' = F / 9

d) F' = K*qA*qB / (d/2)^2 = 4 * K*qA*qB / d^2

F' = 4F

e) F' = K*(3qA)*qB / (2d)^2 = 3*K*qA*qB / 4d^2

F' = 3/4*F

Those are the answers

That's it