physics question - coffee related

**road trip** · 09-06-2006, 11:32 AM

Okay, so say a friend purchases a vacuum-sealed bag of coffee in the high altitudes of Peru and returns it to this sea level that is New Jersey. What happens to the bag? Does it shrivel? Or expand?

**OldLarry** · 09-06-2006, 11:34 AM

This isn't really about coffee, it it?

**Yossarian** · 09-06-2006, 11:34 AM

The plane does not take off!!

**kidwoo** · 09-06-2006, 11:35 AM

It turns into cocaine.

**UTdave** · 09-06-2006, 11:35 AM

Originally Posted by road trip

Okay, so say a friend purchases a vacuum-sealed bag of coffee in the high altitudes of Peru and returns it to this sea level that is New Jersey. What happens to the bag? Does it shrivel? Or expand?

Neither. There should be no air inside it so the only forces on it come from outside. Howerer, say it was just a bag of something packaged at high altitude then the force of the atmoshpere at sea level would be higher than at packaging altitude (force pushing out from within the bag) and the bag would shrivel.

**TeleHoar** · 09-06-2006, 11:37 AM

If it was in your colon the whole time...then nothing.

Otherwise it would shrivel up to resemble Hulk Hogan's testicles or possibly a piece of vacuum wrapped bacon.

**road trip** · 09-06-2006, 11:39 AM

Originally Posted by OldLarry

This isn't really about coffee, it it?

It's that special, finely ground, albino coffee.

....and I like UTdave's answer.

You win me randomly complimenting your subsequent posts even if I disagree with them. Wow. Priceless!

**GoldMember** · 09-06-2006, 11:44 AM

Actually, the bag would still shrivel a little. The external force adds to the internal suction and further compresses the contents. With sea level atmosphere, there is greater external pressure added to the constant internal suction and the contents shrink.

**FrankZappa** · 09-06-2006, 11:49 AM

A cheap plastic bottle of some half filled liquid form / half air (shampoo for example), taken from sea level to high altitude creates a surprising mess.

**splat** · 09-06-2006, 11:55 AM

The answer lies within.

**irul&ublo** · 09-06-2006, 11:58 AM

Originally Posted by splat

The answer lies within.

Mr. Barista....could you put that double half caf carmel cappucino up my ass?

**Core Shot** · 09-06-2006, 12:04 PM

Its actually a trick question.
If you vacuum seal an empty bag, does it shrivel or expand when you change altitude? Answer: Neither.

When you vacuum seal coffee beans, there will be air trapped between the beans as well as inside the beans themselves. it all depends on how much vacuum you apply and how long you leave it.

Real world coffee bean example: Coffee bean bags have one way valves to let gas out but not in. When you put these in your checked luggage, the high atmosphere lets the air out, but when you land air doesn't get back in, so the once loose bag of beans is now all shriveled.

But really, Splat's answer is more descriptive.

**Stymie** · 09-06-2006, 12:05 PM

It would compress a little bit.

several points worth making (ok... not really "worth" making... but I'm going to say them anyway):

1. There is air inside... just not much (I'm assuming the Peruvian's, while probably quite ingeneous, haven't mastered the creation of an absolute vacuum... and even if they did, would they use this ground breaking achievement for coffee bags? ok... maybe).

2. The only force acting on the bag is air pressure. The effect would be the same for any enclosed object (mitigated, of course, by the structural rigidity of said container... wahoo, I got to say "structural rigidity" in a post- 10 points.)

**Mr.Scruff** · 09-06-2006, 12:05 PM

Originally Posted by Yossarian

The plane does not take off!!

DON'T YOU FUCKING DARE!

**pechelman** · 09-06-2006, 12:06 PM

goldmember has the right idea

regardless of how much air is inside of the coffee bag, the greater external atmospheric pressures experienced at lower altitudes than those present in Peru, will cause said container to be compressed.

just imagine that instead of dealing with air, you're in a swimming pool of water. Imagine what would happen when you bring your PBJ in a zip lock bag from the top of the pool to the deep end.

**GoldMember** · 09-06-2006, 12:07 PM

I hate soggy sandwiches.

Even if there is no air, there still is negative pressure (vacuum, suction) inside the bag. That is a constant value. The only variant is the external pressure. With greater external pressure, the overall compression of the contents increases and the bag has shrinkage. Kinda like George Costanza getting into the deep end of the pool with the sandwich.

**phUnk** · 09-06-2006, 12:07 PM

Originally Posted by Mr.Scruff

DON'T YOU FUCKING DARE!

Seriously. Of course the plane takes off. Duh.

**kidwoo** · 09-06-2006, 12:08 PM

Originally Posted by pechelman

just imagine that instead of dealing with air, you're in a swimming pool of water. Imagine what would happen when you bring your PBJ in a zip lock bag from the top of the pool to the deep end.

Oooh.....I just HATE it when the jelly squirts out.

**pechelman** · 09-06-2006, 12:09 PM

Originally Posted by Core Shot

Its actually a trick question.
If you vacuum seal an empty bag, does it shrivel or expand when you change altitude? Answer: Neither.

unless the change in altitude is so great you begin to experience the actual compressibility of the plastic.

Things like this occur in mediums with much higher densities, ie water.

I forget the exact number, but its ridiculous how much the diameter on a submarine's hull decreases due to hydrostatic pressure.

also reference hydroforming

**The AD** · 09-06-2006, 12:10 PM

Originally Posted by UTdave

Neither. There should be no air inside it so the only forces on it come from outside. Howerer, say it was just a bag of something packaged at high altitude then the force of the atmoshpere at sea level would be higher than at packaging altitude (force pushing out from within the bag) and the bag would shrivel.

Anyone who's ever closed an empty disposable water bottle at altitude should have first-hand experience with this. When you descend the bottle is compressed. As soon as you unscrew the top it returns to its normal shape.

I don't agree with the first thing you said, though. Since there's more force acting on the bag at sea level it will be shriveled more than it is at altitude. The pressure inside the bag is zero, so the only thing that matters is the external pressure which will be greater at sea level.

**FrankZappa** · 09-06-2006, 12:13 PM

I think we need to consider weather (pressure) conditions at pt. A and pt. B.

...and, if you drop an open faced PBJ sandwich at the deep end of the pool, which side does it land on? - or is there enough time to intercept?

**The AD** · 09-06-2006, 12:17 PM

Originally Posted by FrankZappa

I think we need to consider weather (pressure) conditions at pt. A and pt. B.

Even if the NJ location is being affected by a category 5 hurricane I think it's safe to say the atmospheric pressure in Peru will be lower.

**summit** · 09-06-2006, 12:47 PM

coffee offgasses over time... this is why gourmet bags have one way valves to let the offgass (CO2 if memory serves) out without letter the flavor destroying O2 in

so yes... trick question

**rideit** · 09-06-2006, 12:50 PM

Chances are equally as good that the coffee was roasted, bagged, and sealed in Lima, at zero altitude, and then shipped back to the highlands for tourist sale.

I know a 'lil' bit about this...