Why is an unopened carton so much harder to shake?

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Wink Grise

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Wink Grise  asked the Naked Scientists:
Hi Chris and Team,

Love the show.

I have a physics question. I don't think it's been covered much or at all, even though it's of course, incredibly important! I can't find much info online, mostly because it's difficult to phrase the question in a search engine. Here goes...

When I shake a new carton of orange juice (the good stuff, no concentrate for me), it is difficult to shake until I break the seal. What's up with that?

The new carton is under a vacuum (well, a tiny vacuum, I know it's hard to get a "good" or "real" vacuum even in outer space...), so I would think there's a good few centimetres for the juice to slosh around free and easy. But when you crack the seal and let air fill the void, you've got this dense gas, so it should be harder to shake now...but it's much easier!

This could be all perception, but others have observed this effect.

What is going on?



What do you think?
« Last Edit: 05/11/2010 18:30:03 by _system »


Offline thedoc

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Why is an unopened carton so much harder to shake?
« Reply #1 on: 10/12/2010 15:26:05 »
We discussed this question on our  show
We took this on as this week's Kitchen Science!
Click to visit the show page for the podcast in which this question is answered. Alternatively, [chapter podcast=2913 track=10.11.28/Naked_Scientists_Show_10.11.28_7585.mp3] listen to the answer now[/chapter] or [download as MP3]
« Last Edit: 10/12/2010 15:26:05 by _system »