Defective mass?
Two carefully prepared specimens of two different materials were manufactured and actually had the same mass as each other (within a negligible error). When they were weighed against each other on a suitable high accuracy pan balance, they didn't balance! Why?
Assume the specimens are solid solids!
Assume the specimens are solid solids!
Labels: funphysics
posted by Chris at
4:03 PM
11 Comments:
The pan balance are flat disks with no means to contain liquid which one of the substances just happened to be, the other solid.
Hi Anonymmous. I hadn't thought of that. I've just amended the question to exclude that reason.
"Assume the specimens are solid solids!"
solid solids, you say? Good... those liquid solids really anger me :/
Anyways... The only thought that occur to me at the moment are the following:
1: The weighing is done in a gravity-free environment.
2: The substances are strong magnets what will repel each other.
3: One of the substances reacts with the metal on the balance pan.
Anywhere close?
Hi Cry Wolf. I'll reveal later why I said solid solids ^^
Gravity is required for pan balances to work.
I hadn't thought of your other ideas. Good tries though.
I thought of the problem while adding a response in the floating hourglass blog.
One of the solids is dry ice which evaporates (or vaporises) faster than whatever the other solid is.
They have the same mass, but they don't weigh the same?
Could the difference be boyancy? or density? Maybe the balance was in heavy air, or water.
If you had equal masses of hydrogen and oxgyen. They would not balance if the scale were in normal air. I know you said solid solids, but I can't think of a solid that would lighter than air.
Ragknot got it - buoyancy differences, courtesy of density differences, is the cause of the discrepancy. The lower density specimen would have a lower weight.
I said solid solid to distinguish from hollow solid, as that could get confusing, and I didn't want to give the whole game away with a better phrase.
I don't know if labs would use vacuums to deal with this, or if they would simply make corrections based on the volume of the specimens and the density of air.
There lowest denity solid that has been made is called aerogel or frozen smoke. Its density is about 3 times that of air. See http://en.wikipedia.org/wiki/Aerogel. There are also a few videos on YouTube about it.
I nicked this from somehwere: Aerogels can actually be made lighter than air by forming them in an atmosphere of helium, resulting in the world's only lighter-than-air solids.
The term solid solid is not acurate in this situation as the material is porous and contains gas. This gas produces the thermal insulating factor that is desired by this material. It would be the same as if the material contained water.
Hi Ragknot. I agree that the word "solid" is not not technically correct and that "gel" is the correct word. Does it come in raspberry flavour?
As a thermal insulator, it is second to none (as far as I can tell). Up to 57 times as good as styrofoam with the right preparation.
It is amazing stuff, I'd love to have a sample to play with.
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