Coulomb's Law and repulsive force

[Soaring Crane]

Homework Statement

Charges q1 and q2 exert repulsive forces of 15 N on each other. What is the repulsive force when their separation is increased so that their final separation is 160% of their initial separation?

a.1.3 N

b.9.8 N

c.8.7 N

d.5.9 N

Homework Equations

F = (k*q_1*q_2)/(r^2)

The Attempt at a Solution

F_2 = [k*q_1*q_2]/[(1.6^2)*(r^2)]

F_2 = F/(1.6^2) = F/2.56

F_2 = 15 N/2.56 = 5.86 N ??

Homework Statement

The force between two very small charged bodies is found to be F. If the distance between them is doubled without altering their charges, the force between them becomes


a.F/2

b.2F

c.F/4

d.4F

Homework Equations

F = (k*q_1*q_2)/(r^2)

The Attempt at a Solution

F_2 = (k*q_1*q_2)/(2r)^2 = (k*q_1*q_2)/(4*r^2)

F_2 = F/4 ?


Thanks.

 

[Kurdt]

Yeah I think you've nailed the inverse square concept.