Monday, February 1, 2010

Helium Luggage

Airline luggage fees have gone out of control lately, and this has lead to a very predictable (and annoying) result: it takes forever to get on a plane because everyone is trying to store all their luggage as carry-ons. Many people would gladly pay the extra money for a ticket so that they wouldn’t have to deal with this frustration. I’d much rather go back to the good old days when we only had to pay a fee if our bags were over 50 lbs. Plus, I could finally use my plan of filling my luggage with helium to beat the system. How much extra weight can you add by filling your suitcase with helium?

My suitcase has dimensions of roughly 1.5 m by 0.75 m by 0.5 m (~4.9 ft by 2.5 ft by 1.6 ft), giving a total volume of 0.56 m3. About half of this is filled with clothes, toiletries, and an alphabetized stack of faculty rejection letters, but that leaves about 0.28 m3 of interstitial space filled with needlessly heavy air. Air has a density of 1.2 kg/m3, but helium only has a density of 0.17 kg/m3. Using these numbers, we can compute the amount of mass we would lose by switching the air with helium:

mass lost = [ (air density) – (helium density) ] · (volume)
= [ (1.2 kg/m3) - (0.17 kg/m3) ] · (0.28 m3)
= 0.29 kg

Ha! I just fit an extra 0.63 lbs in my suitcase. Take that, System!

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