1. Not finding help here? Sign up for a free 30min 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!

Finding the mass of a planet using gravitational acceleration and radius

  1. Nov 22, 2008 #1
    1. The problem statement, all variables and given/known data

    Planet Z is 5000 km in diameter. The free-fall acceleration on Planet Z is 7.00 m/s^2. What is the mass of Planet Z?

    2. Relevant equations

    Well Newton's gravitational law G(M1M2)/R^2
    And I cannot think of much else


    3. The attempt at a solution

    On one of the earlier homeworks we were given a table in which there were fictional planets and their ratios of mass and radius to earth so I tried using

    gG M(earth)/(R(earth))^2 = gG M(z)/(R(z))^2
    Where the "g"s are each planet's free fall acceleration.
    so that the Gravitational constant would cancel and I'd have the Mass of planet Z

    For the mass of the earth I used 5.97E34, for the radius of the earth I used 6387.1 km
    I know that the radius needs to be in meters and would be correctly notated as 6.3871E6

    I don't know how to figure this one out
     
  2. jcsd
  3. Nov 22, 2008 #2

    LowlyPion

    User Avatar
    Homework Helper

    Welcome to PF.

    F = ma = GMm/r2

    a = GM/r2
     
  4. Nov 22, 2008 #3
    Thank you very much
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?