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!

Heavy question; the gravity of a thought experiment

  1. Feb 24, 2014 #1
    Just thinking about gravity. How is the gravity effected by the surroundings of a location?

    Suppose we have a giant farris wheel with very good bearings and we place it in a location; like the Grand Canyon - somewhere with a very steep dropoff; such that say 40% of the wheel is over the cliff. So the buckets that cross the boundary of the cliff have no earth below them for say 2500 feet at least; while the other side is positioned over solid rock/earth. Would there be a large enough difference in the delta of the gravity to cause a spin from the buckets over the solid earth having more pull? I have not worked out the math yet, just a ponder?

  2. jcsd
  3. Feb 24, 2014 #2


    User Avatar
    Science Advisor
    Gold Member

    The local gravitational field varies with the density of local/underground rock formations. Mining companies have been using this information as part of their scientific prospecting technique since Eötvös developed practical devices. See the Wikipedia article on Eötvös.

    But is it enough to move something besides the most delicate of balances? The answer is not so that anybody would notice.
  4. Feb 24, 2014 #3


    User Avatar

    Staff: Mentor

    Gravity doesn't just pull in one direction, it pulls in all directions. So you can't prevent the ground underneath the ferris wheel from pulling on the entire ferris wheel.
  5. Feb 24, 2014 #4


    User Avatar
    Science Advisor

    Of course not. Energy is conserved. It takes as much energy to lift a bucket as you get from dropping a bucket. It doesn't matter if you lift it in some zig-zag direction or straight up.
  6. Feb 25, 2014 #5
    No one side of the wheel would be attracted more than the other, so it would just stop.
    Say it was a very sensitive beam balance hanging over the cliff with equal weights one end would go down and the other up and then stay there what makes you imagine it would spin.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook