I think the latter weighs significantly more, because there is more internal ‘mass’ present compared to an empty bottle. However, an acquaintance of mine doubts this.
Answer
Dear Eric,
Your reasoning is correct, because air also has mass.
The mass density of air at room temperature and at atmospheric pressure (at sea level) is about 1.2 kg/m3 (1.2 g/l).
If you talk about air under pressure (eg 210 bar), the mass density is (210 times) higher.
You can consider three situations:
the diver’s cylinder is open, closed at atmospheric pressure, or is “empty” in the sense that no air will escape if you open it.
b. the diver’s cylinder is filled with compressed air at 210 bar
c. the diver’s cylinder is completely vacuumed: then it is really empty.
Suppose the diver’s cylinder has a mass of 14 kg and a volume of 11 liters, then the total mass is:
a. 14 kg + 11 lx 1.2 g/l = 14.022 kg
b. 14 kg + 11 lx 210 x 1.2 g/l = 16,772 kg
c. 14 kg
Hopefully this answers your question.
Kind regards,
Laurent Vanbeylen
Answered by
Laurent Vanbeylen
Avenue des Pélain 2 1050 Ixelles
http://www.vub.ac.be/
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