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Spinning Toroid shaped objects

  1. Oct 22, 2015 #1
    In our class we were playing with a toroid shaped object made of foam (Probably). While tossing it around, not only was the disc rotating simply. It was well, sort of vibrating. Like one end of the object is up and the other is down then after a small interval the vice versa occurs. What is the main cause of this phenomena ? Is this an example of a toroid shaped example.

    Thank you.
     
  2. jcsd
  3. Oct 22, 2015 #2
  4. Oct 22, 2015 #3

    I have a personal theorem: if it can vibrate in some way, then it will.
     
  5. Oct 23, 2015 #4
  6. Oct 23, 2015 #5
    I think we need more detail on what you observed. How long was this torus in the air? How dense is this foam? Could air resistance be a factor? How symmetric is the shape?
     
  7. Oct 24, 2015 #6
    It was symmetric, there were no visible signs of damage. Torus was in the air for perhaps maximum 1-2 seconds, we were throwing it from one end of the class to the other The distance it traveled was about 10 - 15m. Density of the foam is something I can't comment but it was as squishy as a tennis ball. Can't comment about air resistance. It was non porous, and did not seem to be hollow.
     
  8. Oct 24, 2015 #7
    I'd say distance traveled was too short to make any clear conclusion without sophisticated equipment.
     
  9. Oct 24, 2015 #8
    I will try at larger distances tomorrow when we go back to school.. Thank you :)
     
  10. Oct 26, 2015 #9
  11. Oct 27, 2015 #10
    Hello Anyone ? Please reply ?
     
  12. Oct 27, 2015 #11
    Seeing the video, there's nothing strange going on at all. When thrown, the angular momentum is not aligned with the major axis. This is because the thrower isn't perfectly spinning the torus along this axis.
     
  13. Oct 27, 2015 #12
    We tried, doing many other experiments with this. First one was, throwing it diagonally because I assumed that could be a good answer, it din't work. The torus spun perfectly no vibrations at all. Then we suspected something to do with the velocity inside and outside (Air resistance) We covered it with foil on one side, the vibration increased, when covered on both sides there were no vibrations. Then we threw it vertically, vibrations occured. The video of the other cases has been misplaced. The foil seemed really convincing but we failed to come up with appropriate reasons to why it would go up and down.
     
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