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: Gravitational forces

  1. Mar 12, 2009 #1
    I have this problem i have been trying to solve and can't seem to get it right. The question states:

    The space shuttle is in orbit 396.9 km above the surface of the earth. What is the gravitational force on a 0.64 kg sphere inside the space shuttle?

    mass earth = 5.98x10^24 kg
    radius of earth = 6.37x10^6 m

    I've tried using the equation F= (G*M*m)/r^2 and the answer i got was about 5.57 N

    for the distance above earth i converted the units and added them to the earth's radius so I'm not sure what I could be doing wrong.

    is it possible that i am using the wrong equation all together?
    Last edited: Mar 12, 2009
  2. jcsd
  3. Mar 12, 2009 #2
    r is defined as being the distance between the two point masses.

    I might be wrong, but for this problem, would you not just use the distance from earth as r?
  4. Mar 12, 2009 #3
    F = GMm/r^2 , G is the universal gravity, M is mass of the object acting the force,
    m is the mass of the object that the force is acted upon, r is the distance between the center of the earth and the center of the object in space.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook