If two electrically charged objects attract each other with a force of 1.0N when they are 5.0cm apart, what will be the force between them when they are 1.0cm apart?
The force is inversely proportional to the square of the distance between them, so:
F2/F1 = (r1/r2)2.
Here you have r1 = 5cm, r2 = 1cm, F1 = 1N
Can you take it from here?