Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Center of mass / gravity

  1. Feb 8, 2008 #1
    Can anyone give me an object where the center of mass and the center of gravity are in different locations?
  2. jcsd
  3. Feb 8, 2008 #2
    The center of gravity is not an intrinsic property of an object. It depends on the gravitational field the object is in. In the gravitational field of a spherical object (like, say, the Earth), and object's center of gravity will always be slightly below its center of mass; but, the farther it is from the center of the gravitating body, the smaller this difference.
  4. Feb 8, 2008 #3
    why is it below and why does this get smaller with distance?
  5. Feb 8, 2008 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Because the gravitational field is not uniform: It's stronger the closer you are to the spherical object, so the lower half is pulled more strongly than the upper half. Since the field falls off inversely with the square of the distance, the farther away you are the less it matters.

    Note that for ordinary-sized objects near the earth's surface, earth's gravity can be considered uniform for practical purposes. That's why many introductory texts treat "center of gravity" as synonymous with "center of mass".
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook