Force:

$\overline{){\mathbf{F}}{\mathbf{=}}\frac{\mathbf{G}\mathbf{M}\mathbf{m}}{{\mathbf{R}}^{\mathbf{2}}}}$

Taking the mass of the star to be M, the mass of the planet 1 to be m_{1}, the mass of planet 2 to be m_{2}, R_{1} be the distance between the star and planet 1, and R_{2} be the distance between the star and planet 2:

The gravitational force of a star on an orbiting planet 1 is F_{1}. Planet 2, which is twice as massive as planet 1 and orbits at twice the distance from the star, experiences gravitational force F_{2}.

What is the ratio F_{2}/F_{1}? You can ignore the gravitational force between the two planets. Express your answer using two significant figures.

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What scientific concept do you need to know in order to solve this problem?

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