Two massive, positively charged particles are initially held a fixed distance apart. When they are moved farther apart, the magnitude of their mutual gravitational force changes by a factor of n. Which of the following indicates the factor by which the magnitude of their mutual electrostatic force changes?
a. 1/n2
b. 1/n
c. n
d. n2

c. n

The magnitude of the gravitational force is given by Newton's law of universal gravitation:

Here G is the gravitational constant, are the masses of the particles and d is the distance between them.

The magnitude of the electrostatic force is given by Coulomb's law:

Here k is the Coulomb constant, are the chargues of the particles and d is the distance between them.

As can be seen, both forces are inversely proportional to the square of the distance. Thus, the factor is the same in both cases.

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