- #1
lloyd709
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- TL;DR Summary
- I think a published experiment that demonstrates the weighing of air is incorrect and actually only demonstrates that compressed air weighs more than non compressed air.
I've just purchased a book of child scientific experiments and it has an experiment that is titled 'Weigh some air'. It shows that if you make a scales with a piece of wood and a pivot and then balance two empty balloons on a either end and then fill one of the balloons with air the scales will tip demonstrating the weight of the air.
Something didn't seem quite right to me and after giving it some thought I've come the conclusion (that my more highly physics qualified friend disagrees with) that the reason the scales tip is because the air inside the balloon is compressed slightly and therefore has higher density and less buoyancy within air.
Even though the balloon filled with air has more mass relative to the unfilled balloon it still actually weighs the same when weighed in air because 'weight' depends not only on gravity and mass but also on the fluid or gas that the weighing takes pace in (hence why objects 'weigh' less when weighed in water).
The other way I'm thinking about this is that if you somehow had a rigid container made of a hypothetical material that had the same weight/volume ratio as air (so that it 'weighed' nothing in air) and filled it with air (so the air was uncompressed) than it would still weigh nothing no mater how big you made the container.
I'm getting a lot of stick from my friend on this (he's basically calling me a numpty) so would be great to hear your opinions (a lot of beer depends on it!)
Something didn't seem quite right to me and after giving it some thought I've come the conclusion (that my more highly physics qualified friend disagrees with) that the reason the scales tip is because the air inside the balloon is compressed slightly and therefore has higher density and less buoyancy within air.
Even though the balloon filled with air has more mass relative to the unfilled balloon it still actually weighs the same when weighed in air because 'weight' depends not only on gravity and mass but also on the fluid or gas that the weighing takes pace in (hence why objects 'weigh' less when weighed in water).
The other way I'm thinking about this is that if you somehow had a rigid container made of a hypothetical material that had the same weight/volume ratio as air (so that it 'weighed' nothing in air) and filled it with air (so the air was uncompressed) than it would still weigh nothing no mater how big you made the container.
I'm getting a lot of stick from my friend on this (he's basically calling me a numpty) so would be great to hear your opinions (a lot of beer depends on it!)