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!

Acceleration due to gravity for a hypothetical planet

  1. Feb 25, 2010 #1
    1. The problem statement, all variables and given/known data
    A hypothetical planet has a radius 2.5 times that of Earth, but has the same mass. What is the acceleration due to gravity near its surface?

    R(earth)= 6.38 x 10^4 m
    M(earth)= 5.98 x 10^24 kg
    G= 6.67 x 10^-11

    2. Relevant equations

    3. The attempt at a solution
    I did: (6.67 x 10^-11)(5.98 x 10^24kg) / [2.5(6.38 x 10^4m)]^2
    and got 15,708, but know this is wrong since the answer is near only 15.
  2. jcsd
  3. Feb 25, 2010 #2
    The radius of earth that you have looks like it's supposed to be kilometers.

    Edit: Actually, no because earth's radius is actually 6378 km so the exponent is just messed up.
  4. Feb 25, 2010 #3
    Okay I just looked it up, the radius in km is 6.38 x 10^4, and the radius in meters is 6.38 x 10^6.

    I used this instead and it worked! Thank you for pointing this out for me, and the answer was actually 1.5 m/s^2, not 15.
  5. Feb 25, 2010 #4
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Acceleration gravity hypothetical Date
Finding Acceleration Due To Gravity Jan 28, 2018
Apparent Weight Problem Jan 17, 2018
Vertical Circles Centripetal Acceleration Nov 30, 2017
Acceleration and Gravity with Circular Motion Nov 1, 2017