Solution to 1992 Problem 4


Let m be the mass of the point mass. Then, for r\geq R,
\begin{align*}F(r) = \frac{G m M_E}{r^2}\end{align*}
Therefore,
\begin{align*}\frac{F(R)}{F(2R)} = \frac{\frac{G M_E}{R^2}}{\frac{G M_E}{((2R)^2}} = \boxed{4}\end{align*}
Therefore, answer (C) is correct.


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