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

Apple falling to ground

  1. Jan 12, 2010 #1
    When an apple falls to the ground does it not exert some gravity of it's own on the earth and thus shortening the distance it falls? Why is it always assumed the earth does not itself move in physics problems?
  2. jcsd
  3. Jan 12, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Estimate the earth's acceleration due to the apple's gravitational pull. Then you'll see why it's ignored.
  4. Jan 12, 2010 #3
    The idea of ignoring negligible calculations is to make it easier for students who are introduced to these concepts to make the calculations. However I think it should still be said to the students that the apple is causing the earth to undergo a very very very small acceleration, so that they can be reminded that forces affect both objects.
  5. Jan 12, 2010 #4
    Thanks for replying!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook