Two point masses, each of mass M, are separated by a distance R. The gravitational force between them is F. If the distance is doubled to 2R, what is the new gravitational force?
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Correct answer
A. F/4
Principle or equation
Newton's law of universal gravitation: F = G M1 M2 / r^2. Force is inversely proportional to the square of the distance.
Why this answer is correct
If r is doubled, the denominator becomes (2R)^2 = 4R^2, so the force becomes F/4.
Example
If the distance between two masses is tripled, the force becomes F/9.
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