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Is a pressurized air object heavier?
In other words, is an object heavier when it contains compressed air
than when it's empty? For example, if I have a tire and weigh it
before pumping it full of air, will it be heavier after it's pumped
up? I say NO. A friend of mine insists it will be heavier once it's
filled with air. Who is right?

This is one of those fun topics that no one can agree on, and would
require a very accurrate scale that would most likely need to measure
down to the milligram.

Note: This would be regular compressed air from an air compressor, not
helium or another gas, which might make it lighter (even though I
highly doubt a tire full of air would float).

Mark


I guess someone missed physics class.

Standard air (70 degrees at Sea Level and 0% Relative Humidity) is
13.33 cubic feet per pound. That is at 14.7 Pounds per Square Inch
Absolute (PSIA). That is pressure as related to a vacuum. If you
pressureize an object with air at 32 PSI Guage, that is (14.7+32) PSIA
= 46.7 PSIA. The pressurized air would weigh 3.1769 times as much as
Standard Air. Standard Air weighs .075 pounds per cubic foot. The
pressurized air weighs .075 * 3.1769 = 0.2382675 pounds per cubic foot.
That is a difference of 0.1632675 pounds per cubic foot. So if you
had 5 cubic feet of volume in a tire, the difference in weight would be
5 * 0.1632675 = 0.8163375 or almost a pound heavier. Of course if you
were using something besides Standard Air as a base, the air would have
a different starting weight. For example, colder air would be denser
and would weigh more. If your scale could weigh in increments of 1/10
pound, it would show you the difference.

Stretch