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In this case, the force is inversely proportional to the distance squared. The charges are not changed. The distance is altered from 2.0 cm apart to 8.0 cm apart (4 times as far, which shows that the force is a ratio of 1/16). The initial force was 1,0N. Multiply it with 1/16 and you get the answer: 1,0N*(1/16) =

That's one way to solve it just by using your knowledge and coming to that conclusion.

Here's another way.

Since the force is inversely proportional to the distance squared, we can conclude that: F1/F2 = (r2^2)/(r1^2)

F1 = 1,0N

r1 = 2,0cm = 0,02m

r2 = 8,0cm = 0,08m

Add the values to the equation:

1/F2 = (0,08^2)/(0,02^2)

1 = F2*(0,08^2)/(0,02^2)

F2 = 1/((0,08^2)/(0,02^2))

Good luck with your studies!