Question

Which of the following changes would increase the force between two
charged particles to 9 times the original force?
A. Decreasing the distance between the particles by a factor of 3
B. Decreasing the amount of charge on one of the particles by a
factor of 9
C. Increasing the distance between the particles by a factor of 3
D. Increasing the amount of charge on each particle by a factor of 9

Answer 1

The answer is A. Decreasing the distance between the particles by a factor of 3.

The Universal Law of Gravitation is :

F = Gm₁m₂ / r² (where 'r' is the distance between them)

Since force is inversely proportional to the square of the distance between them, distance has to be decreased by a factor of 3 to increase the force to 9 times the original force.