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: Gravitation Problem

  1. Apr 21, 2009 #1
    The problem statement, all variables and given/known data
    A 11 kg satellite has a circular orbit with a period of 1.0 h and a radius of 4.9 × 10^6 m around a planet of unknown mass. If the magnitude of the gravitational acceleration on the surface of the planet is 41 m/s^2, what is the radius of the planet?

    The attempt at a solution
    I used the formula:
    (4pi^2 Rs^3) / (a T^2) = Rp^2

    I'm on my last try.
    I got 177000000 and then 935000.
    I know the formula is right for sure.
    I'm not sure what's going on with my calculations. It's basic algebra, easy stuff, but I'm making some mistake... >.>
    Last edited: Apr 21, 2009
  2. jcsd
  3. Apr 21, 2009 #2
    What You wrote seems right...
    What did You plug for T?i hope 3600sec
    i got 2956411 meters
    Last edited: Apr 21, 2009
  4. Apr 21, 2009 #3


    User Avatar
    Homework Helper

    The first answer you got was because you didn't square the time. I am unsure how you got to the second answer, however I do get the same answer as Dweirdo.
  5. Apr 21, 2009 #4
    Okay I don't know how I got that second one either.
    I kept plugging in the numbers and got that second answer.
    For some reason, after I read Dweirdo's post, I plugged it in again and this time it worked.
    Don't know what I did back then but thank you very much!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook