1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Kepler's law?

  1. Oct 17, 2008 #1
    Planet X orbits the star Alpha with a 'year' that is 200 earth days long. Planet Y circles Alpha at nine times the distance of planet X. How long is a year on planet Y?

    I know that I have to use the kepler's law : T^2 = (4pi^2/GM)r^3
    but I'm not too sure how to do solve this...
    Please help!
  2. jcsd
  3. Oct 17, 2008 #2


    User Avatar
    Homework Helper

    So T12/r13 = T22/r23
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook