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Posers and Puzzles

Posers and Puzzles

  1. Subscriber sonhouse
    Fast and Curious
    08 Jan '06 16:43
    you have a centrifuge big enough to hold a 10 foot long cylinder
    about 3 feet in diameter. It is filled with standard Atm. You place a
    helium balloon in the center of said cylinder and start it spinning,
    What happens to the balloon?
  2. Standard member Wibble Wobble
    Action barbie
    08 Jan '06 17:05
    Originally posted by sonhouse
    you have a centrifuge big enough to hold a 10 foot long cylinder
    about 3 feet in diameter. It is filled with standard Atm. You place a
    helium balloon in the center of said cylinder and start it spinning,
    What happens to the balloon?
    Spins?
  3. Subscriber sonhouse
    Fast and Curious
    08 Jan '06 22:19
    Originally posted by Wibble Wobble
    Spins?
    I'll give you that, but does it move anywhere else?
  4. 08 Jan '06 22:36
    Originally posted by sonhouse
    I'll give you that, but does it move anywhere else?
    moves toward wall
  5. Subscriber sonhouse
    Fast and Curious
    08 Jan '06 23:28
    Originally posted by ketch90
    moves toward wall
    Expand on That. What wall? The wall of the spinning cylinder?
    Also you know the whole cylinder is spinning as if on a rope, in this
    case the boom, so it has to be counterbalanced completely on
    the other side, its not spinning around its own center.
  6. 09 Jan '06 01:05
    ok: base is resting on x-y plane. is it spinning around the z-axis or the x/y-axis?
  7. Subscriber FreakyKBH
    Acquired Taste...
    09 Jan '06 02:14
    Originally posted by sonhouse
    you have a centrifuge big enough to hold a 10 foot long cylinder
    about 3 feet in diameter. It is filled with standard Atm. You place a
    helium balloon in the center of said cylinder and start it spinning,
    What happens to the balloon?
    Is it a Mickey Mouse balloon, with ears on it? This is important in my calculations.
  8. 09 Jan '06 11:29 / 1 edit
    I would have thought it would start spinning due to air currents in the cylinder causing it to spin. The balloon could then move in any direction due to chaotic effects. Once it hits any wall it would then be forced to one of the ends by centrifugal force.

    Edit: The balloon will expand slightly as well while in the centre, because the centrifugal force would cause some of the air to also move towards the ends reducing the pressure in the centre.
  9. 09 Jan '06 19:26
    Edit: The balloon will expand slightly as well while in the centre, because the centrifugal force would cause some of the air to also move towards the ends reducing the pressure in the centre.[/b]
    there is not really any such thing as centrifugal force.
    does the baloon stay still in relation to outside of the cylinder, but spin in relation to the inside of the cylinder?
  10. 09 Jan '06 22:46
    Originally posted by i am scientists
    there is not really any such thing as centrifugal force.
    Well, there is an opposite reaction (this can be called centrifugal force) to the centripetal force which is a force directed towards the centre of axis of rotation. This opposite reaction is more easily apparent though. I was just being conservative with my choice of words.
  11. Subscriber sonhouse
    Fast and Curious
    09 Jan '06 22:58
    Originally posted by i am scientists
    there is not really any such thing as centrifugal force.
    does the baloon stay still in relation to outside of the cylinder, but spin in relation to the inside of the cylinder?
    I think I said the cylinder is not spinning on its axis, either one.
    Its hanging totally out and spun in total around like the big arm of
    the flight G simulators, picture that arm as containing said cylinder.
    It would be a lot better with a drawing for sure.
    So under those conditions, say its giving the equivalent of one G
    of force, what happens to the balloon?
  12. 09 Jan '06 23:51 / 1 edit
    Originally posted by sonhouse
    I think I said the cylinder is not spinning on its axis, either one.
    Its hanging totally out and spun in total around like the big arm of
    the flight G simulators, picture that arm as containing said cylinder.
    It would be a lot better with a drawing for sure.
    So under those conditions, say its giving the equivalent of one G
    of force, what happens to the balloon?
    Think I know what you are describing. The balloon would actually move towards the axis of rotation. The air would increase in pressure at the end of the cylinder (end as in direction away from the axis of rotation). The balloon would oppose this force due to gas bouyancy (tend towards the axis of rotation where the air density would be less). This is because of the low gas density of the helium in the balloon.

    I think this is correct.

    Edit: Based on the original idea I thought you had where the cylinder was actually rotating in my previous post. The balloon would stay in the centre because that is where the air density will be least, not go towards one of the ends as I previously described. Not related to the current scenario in this thread but still a point I needed to correct.
  13. Subscriber sonhouse
    Fast and Curious
    11 Jan '06 06:27
    Originally posted by lausey
    Think I know what you are describing. The balloon would actually move towards the axis of rotation. The air would increase in pressure at the end of the cylinder (end as in direction away from the axis of rotation). The balloon would oppose this force due to gas bouyancy (tend towards the axis of rotation where the air density would be less). This is because ...[text shortened]... d. Not related to the current scenario in this thread but still a point I needed to correct.
    Give the man the golden ring! Thats what would happen. I told this
    one to my son Kevin and he had the answer before I could even
    finish telling it. He is used to my puzzles by now.
    I had one where the same kind of cylinder was on a space ship
    way away from stuff so basically at zero gravity and then you do the
    same thing, put a balloon dead center, then fire a rocket at one end.
    What happens to the balloon? Same thing, If it were a bowling ball
    it would go to the end where the rocket is of course but a helium
    balloon goes the other way for just the reason you said:
    pressure differential is what gives the lifting force so I was pointing
    out what Einstein said a long time ago: you can't tell the differance
    between gravitation and acceleration so if you take the cylinder and
    just hold it upright, gravity does the pressure gradient, if you spin it,
    centripital does it, if you fire up a rocket, acceleration does it.
    All three ways end up with a pressure gradient. I think I have run this
    one into the ground!
  14. 11 Jan '06 17:47
    Originally posted by i am scientists
    there is not really any such thing as centrifugal force.
    In the cylinder's frame of reference, there is.
  15. Standard member Trains44
    Full speed locomotiv
    11 Jan '06 17:49
    Originally posted by sonhouse
    you have a centrifuge big enough to hold a 10 foot long cylinder
    about 3 feet in diameter. It is filled with standard Atm. You place a
    helium balloon in the center of said cylinder and start it spinning,
    What happens to the balloon?
    Probably get dizzy. No?