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Bunny in a Vacuum

  1. Mar 22, 2006 #1
    A balloon Easter bunny is put into a vacuum chamber that is originally at room temperature and pressure. The air in the vacuum is evacuated. The air inside the bunny is not evacuated and the bunny is not sucked down the tube. What happens to the rabbit and why?

    This question was on a test I took last night. I didn't attempt it because the test was timed, I couldn't explain it, and I was tired.:rofl: We finished up the module as well as the entire marking period but I'm curious. Why wouldn't the rabbit get sucked down the tube? Was/Is it as simple as, "The air inside the bunny is being trapped inside it by the balloon and it didn't go down the tube because it was too large."?:blushing:

    (Sorry for the strange title, I couldn't think of anything else.:tongue: )
     
  2. jcsd
  3. Mar 22, 2006 #2

    Hootenanny

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    Think about pressure. The bunny would burst. She if you can use pressure and force to explain why...:smile:
     
  4. Mar 22, 2006 #3
    The air inside the bunny is not evacuated and the bunny is not sucked down the tube.

    Are you sure? That makes it sound like the bunny wouldn't even bust...:rofl:
     
  5. Mar 22, 2006 #4

    DaveC426913

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    It woudn't. The Bunny would expand to fill the volume of the chamber. You'd have a chamber whose walls are lined with latex. By that time, the air inside the balloon would be too rarified to push the part over the evacuation tube down the tube.


    P.S. Possibly a trick question: nowhere does it say the balloon is filled or sealed. Perhaps it's a "virgin" balloon?
     
  6. Mar 22, 2006 #5
    Why would it do that? Is it because the pressure that was outside the balloon is decreasing, allowing it to expand? I kind of feel like I'm going out on a limb with that guess.:smile: And what do you mean by, "Perhaps it's a "virgin" balloon?":rofl:
     
  7. Mar 22, 2006 #6

    DaveC426913

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    Well, I hope you're not guessing :uhh: . You should know what a balloon with air in it will do as ambient pressure changes.
    I mean perhaps it had no air in it in the first place, in which case, there'd be no air to come out of it, and it would not "blow" toward the vacuum tube.

    This is highly unlikely to be the answer they were looking for, unless you're reading about brain teasers rather than legit school assignments.
     
  8. Mar 22, 2006 #7

    Bystander

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    Might be talking about the Mylar "balloons" from "party stores;" if the bunny ain't inflated, and is sealed when placed in the chamber, when the chamber is evacuated, the bunny inflates. That's the first part. If it happens to be sitting in the air stream during the atmospheric to 1 mm Hg part of the evacuation process, yes, it is going to be drawn to the evacuation port. If it survives the early part of the process, it'll be lying on the floor of the chamber (denser than remaining air in chamber), and if the Mylar is strong enough (not a whole lot of air trapped in it), that air is confined in a "sealed" container of non-constant volume, and can be recovered.
     
  9. Mar 22, 2006 #8

    Hootenanny

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    Depends on how big the vacume chamber is and the ultimate tensile strength of the balloon/
     
  10. Mar 23, 2006 #9
    And why, may I ask, should I know "what a balloon with air in it will do as ambient pressure changes"?:uhh: If I knew, I wouldn't be asking now would I?:wink: I've never even heard of "ambient pressure" until now.

    No, it's a real question, not a brain teaser.:rofl: It's blown up as well, there was a drawing and it was fully inflated...or at least I think it was. That's what I thought upon reading the question and seeing the picture.
     
  11. Mar 23, 2006 #10

    HallsofIvy

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    What do you mean by "fully inflated"? Are you thinking that once you have "blown up" a balloon, it is impossible for it to get any bigger? It's the difference between pressure inside and pressure outside that makes a balloon get big. There is no difference between lowering the pressure outside the balloon and increasing the pressure inside the balloon (putting more air in it). What might stop a balloon from getting larger as you blow more air into it?

    (When I first read the title "bunny in a vacuum", my first reaction was "My God, what kind of evil person is this!")
     
  12. Mar 23, 2006 #11

    Bystander

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    Run down to the novelty store. Buy a Mylar balloon. Buy a rubber balloon. Compare the elasticity of Mylar to rubber.

    Yes. Mylar balloons can be "fully inflated" and have nearly fixed volumes that are nearly independent of "ambient pressure" at earth surface filling densities. Remember Echo?
     
  13. Mar 23, 2006 #12

    NateTG

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    The bunny dies....

    There is a pressure difference between the inside of the bunnys lungs and the inside of the Bell jar that pushes outward at 19 PSI or so. That's most likey strong enough to cause massive internal damage, and maybe some explosive effects.

    Of course, the bunny isn't actually likely to die of explosive decompression. Instead, gasses that are normally disolved in the blood like Carbon Dioxide and Nitrogen would come out of solution and bubble through the veins causing massive strokes and destroying the longs. For humans this is very painful and quite lethal.
     
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