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## Homework Statement

Two remote planets consist of identical material, but one has a radius twice as large as the other. IF the shortest possible period for a low altitude satellite orbiting the smaller planet is 40 minutes, what is the shortest possible period for a similar low altitude satellite orbiting the larger one? Answer in minutes.

## Homework Equations

volume of sphere=4/3 ∏r

^{3}

speed=distance/time

E

_{k}=-1/2 E

_{g}

## The Attempt at a Solution

r

_{B}=2r

_{A}

time

_{A}=2∏r/V

_{A}

40=2∏r/V

_{A}

Don't really know how to move on from here? I know I have to find the time taken for the satellite to orbit planet B.

T

_{B}=2∏(2r

_{A})/V

_{B}

I don't know V

_{B}, how would I find that?