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## Homework Statement

Two identical spaceships are sent to explore a planet with two moons. Each spaceship orbits one of the moons.

a)The orbital radii are observed such that the spaceship have the same period. What is the relative mass of the two moons if the two radii differ by a factor of 2.

b) If the two moons have a similar radius, what does this imply about their density? What does this tell you about how the moons were created?

## Homework Equations

a=v^2/r

v=2pi^2/T

ma=Gm(Mearth)/r^2

F=Gm1m2/r^2

## The Attempt at a Solution

a) 4pi^2/T^2=G(Mearth)/r^2

since T is the same, T=1

b) If the two moons have similar radius, then they should have different densities (if the relative masses are different in part a)