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Is this possible for hanging objects from spinning sphere?

  1. Mar 7, 2015 #1
    This youtube clip has a ride that is a spinning sphere with objects hanging by strings from the surface.

    (see at about 0:55)

    This is the only ride in the video I think is theoretically impossible (the others seem like they could be done but would be dangerous and/or costly). I think it's theoretically impossible because there is no way objects on the top hemisphere could stick straight up, with their strings perpendicular to the surface of the sphere, without some external force like wind blowing from the ground up. If you deconstruct the sphere, which is only spinning along the z-axis in the theta direction, it is like many thin rings stacked on top of each other. If you take any one of those rings with an object hanging from it and spin the ring (only in the theta direction), the highest up off the ground it could be is (just short of) the height of ring from the ground, with only natural forces acting on it.

    My friend thinks that these objects could be sticking out with the strings perpendicular to the surface of the sphere no matter where they are on the sphere, except at the very top, if the sphere is spinning fast enough.

    I think that even if the strings were infinitely strong and the sphere were spinning infinitely fast, the strings that the objects were hanging from would be perpendicular to the ground (not the surface of the sphere).

    Am I right?
  2. jcsd
  3. Mar 7, 2015 #2


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    Staff: Mentor

    Yes, everything is correct.

    You could use fixed beams instead of strings for the upper sections to get seat positions above the topmost part of the sphere.
  4. Mar 8, 2015 #3
    You realize that nothing in that video is real right?
  5. Mar 8, 2015 #4


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    You are correct. Your friend is wrong.

    If those tethers are not rigid, the highest that any particular pod could go is with its tether parallel to the ground.

    The only way the idea could be realized is to make the tethers rigid AND to mechanically control the angle at which they emerge from the sphere.
  6. Mar 8, 2015 #5


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    It's still hilarious: Gravity is an error.
  7. Mar 8, 2015 #6

    Vanadium 50

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    I agree.
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