Solving Planetary Motion: X & Y's Circular Orbits

[lempkema]

Homework Statement

Planets X & Y travel in circular orbits around the same star. The ratio of the radii of their orbits is 5:2. 5 years after the planets were aligned, planet x has rotated 92.6 degrees. how many degrees has y traveled in the same amount of time?

Homework Equations

v^2=GM/R

Wx=phix/t; Wy=phiy/t

phix= angular of X after t time
phiy= angular of X after t time

The Attempt at a Solution

I just keep getting the wrong answer. I try transferring the ratio of radii to the angular velocities, but i must be doing it wrong.

 

[Borek]

Check Kepler's third law.

 

[lempkema]

thank you so much, that made to ratio a lot less difficult to apply!

 

[Borek]

Note, that third law can be derived from the F=GMm/r^2.