Timeline for Why does sound travel faster in iron than mercury even though mercury has a higher density?
Current License: CC BY-SA 4.0
15 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Feb 29, 2020 at 12:56 | history | edited | user59991 | CC BY-SA 4.0 |
It is not permissible to use abbreviations for unit symbols or unit names. Do not write “sec” (for either s or second).
|
| Sep 19, 2019 at 6:29 | comment | added | Agnius Vasiliauskas | @JohnRennie 𝐾 is the bulk modulus, which is a measure of how much force is required to compress the material Not exactly. Bulk modulus is defined as $$ K=-V{\frac {dP}{dV}} $$, so it measures materials resistance to compression - how much it's pressure increases when volume is decreased. What you are talking about is inverse of bulk modulus, aka "compressibility" - change in volume under applied pressure. And no, $K$ applies not only to solids, but to fluids and gasses as well, because almost everything is compressible | |
| Mar 29, 2014 at 10:03 | vote | accept | Abhishek Mhatre | ||
| Mar 5, 2014 at 18:51 | comment | added | Patrick M | @JohnRennie I would have to leave any deeper math to you, as I am but a layman. I did post my thoughts as a separate answer; hopefully they provide some understanding to others such as myself. | |
| Mar 5, 2014 at 17:47 | comment | added | John Rennie | @PatrickM: thanks :-) However I feel that if we were going to extend the answer (and I'm not sure we should) then a more mathematical treatment would be better. | |
| Mar 5, 2014 at 17:26 | comment | added | Patrick M | @JohnRennie I suggested an edit after attempting to understand it myself. Feel free to correct any inaccuracies or revert it if you still don't think this is the correct place to answer 'why'? | |
| Mar 5, 2014 at 17:24 | review | Suggested edits | |||
| Mar 5, 2014 at 17:46 | |||||
| Mar 5, 2014 at 9:32 | comment | added | John Rennie | @ThorbjørnRavnAndersen: we regard the moduli as fundamental because they are the same for all lumps of iron (larger than a few thousand atoms) and they are directly related to interatomic forces. By contrast the velocity depends on the size and shape of the piece of iron. In my answer I referred to the fact that a long thin rod gives a different speed of sound to a more symmetric piece. | |
| Mar 5, 2014 at 9:19 | comment | added | John Rennie | Re comments on expanding the answer: I didn't expect the question to attract anything like this amount of attention. I'm not sure expanding this answer to a full description of the theory of sound propagation is appropriate, but if anyone wants to ask a related question I'd be happy to answer. Please read the Wikipedia link first though, and try to make any new question specific rather than a generic tell me how it works. | |
| Mar 5, 2014 at 9:18 | comment | added | Thorbjørn Ravn Andersen | @JohnRennie so you agree? | |
| Mar 5, 2014 at 9:17 | comment | added | John Rennie | @ThorbjørnRavnAndersen: $K$ is the bulk modulus, which is a measure of how much force is required to compress the material. $G$ is the shear modulus, which is a measure of how much force is required to bend the material. These are characteristics of the solid. | |
| Mar 5, 2014 at 9:14 | comment | added | Thorbjørn Ravn Andersen | Is it correct that K and G are medium specific constants, which basically have been measured originally? If so, are you basically not saying that the speeds are different because we have measured them to be different? | |
| Mar 5, 2014 at 3:13 | comment | added | GreenAsJade | I agree with PatrickM. This doesn't tell us why, it just tells us how to compute it. The answer to "why?" is that the speed depends not only on density, but also a mysterious thing call bulk modulus, which represents ... what? | |
| Mar 4, 2014 at 19:00 | comment | added | Patrick M | This answer would be improved by giving easy to understand definitions of bulk modulus and shear modulus, and how they relate to/differ in different states of matter. | |
| Mar 4, 2014 at 14:02 | history | answered | John Rennie | CC BY-SA 3.0 |