We have that the formula for the gravitational force is:[tex]F= \frac{Gm_1 m_2}{r^2} [/tex].
Suppose now that their distance is R, their masses M and m and suppose their distance becomes 2R
500N=GMm/R^2.
We want to calculate GMm/(2R)^2=GMm/4R^2. We know from the first equation though what this is; this is 500/4=125 N. Thus, the power between them is 1/4th of the power they had at the initial distance.
