Two charged balls which are near each other will exert a force on each other: attractive if they are oppositely charged, and repulsive if they are similarly charged. The magnitude of the force is given by
where F is in N, k is a constant 9 x 109 N m2/C2, q1 and q2 are the charges on the balls measured in C, and r is the distance between the balls in m.
In a certain experiment two balls are both given a charge q, they are set a distance r away from each other, and the force between them is recorded. Which graph best represents the relationship between F and q?