You have a metal water bottle entirely filled with a vacuum and you have a rubber party balloon (lets make it red). How can you use only the bottle to inflate the balloon with the air surrounding you. (The balloon does not have to inflate in the normal shape)


1 Answer 1


Well ....

To be "filled with a vacuum" the metal water bottle has to have been evacuated of everything, including air, and closed off to prevent the air from going back in.
If you put the balloon over the seal of the water bottle and then release the seal—assuming, since there's no other meaningful way to do what is requested here, that there is a way to release the seal—then the vacuum will draw the balloon into the metal bottle, turning it inside out in the process. But the confines of the balloon will indeed now be filled with the air surrounding it, and you.

If you insist that

the balloon not be inside-out and thus not inflated in a usual manner, you can turn it inside out before putting it on the bottle. This isn't particularly difficult to do for most balloons.

At this point

you can detach the balloon from the bottle and tie it off. With a little care in how you do this, you can keep most of the air inside it, so that it's now indeed inflated to just smaller than the rough limits of the size of the metal bottle, so it can still be pulled out of it.

  • $\begingroup$ I don't think that the lateral-thinking tag applies here, it's purely physics. $\endgroup$ Commented Aug 27, 2019 at 12:18
  • $\begingroup$ Purely physics, yes, but applied in an unusual way. I think the tag is fitting, even if not strictly required. $\endgroup$
    – Rubio
    Commented Aug 27, 2019 at 12:30
  • $\begingroup$ I added it in case someone had a different answer, as I was willing to see that as well. $\endgroup$
    – B-K
    Commented Aug 28, 2019 at 10:35

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