I think Randall mentioned this at one point but I never really understood it. Is it something like on a molecular level they’re still taking some time to push in to each other? It’s so damn trippy. At what point is my long pole going to have a delay when I push it? It sounds unreal
Comment on Why can't a liquid move faster than the speed of sound in that medium?
rikudou@lemmings.world 1 day ago
You already got some answers, but I thought of something you might find interesting: if you had a multiple kilometers long pole in a vacuum and pushed on it, the push itself would propagate at the speed of sound!
Meaning the other end wouldn’t really move immediately, but it would instead take multiple seconds or even minutes if the pole is large enough. If it’s made of oak and is 9 km long, it would take around 3 seconds (the speed of sound in oak is around 3 km/s IIRC).
pineapplelover@lemmy.dbzer0.com 14 hours ago
rikudou@lemmings.world 13 hours ago
Basically, when you push something, you push molecules, those in turn push the other molecules etc., that’s what it is.
The delay is there every time, it’s just usually really fast, the speed of sound in solid mediums is much bigger than the speed of sound in air.
pineapplelover@lemmy.dbzer0.com 5 hours ago
There’s more delay in solid mediums than air?
rikudou@lemmings.world 2 hours ago
No, the faster the speed of sound, the less delay there is.
ryannathans@aussie.zone 21 hours ago
Do incompressible materials therefore have extremely high speed of sound?
eRac@lemmings.world 19 hours ago
Yes. Nothing is truly incompressible. The speed of sound can be viewed as a measure of how much a material can squish on the atomic level before the next atoms move.
Successful_Try543@feddit.org 14 hours ago
Nothing is truly incompressible.
Exactly. One usually speaks of quasi-incompressibility when the resistance against compression (bulk modulus) is much greater than the resistance against shear (shear modulus), which is oft the case for liquids such as water.
However, water has a lower resistance against compression (2 GPa) than e.g. steel (160 GPa), which is considered a compressive material.
xavier666@lemmy.umucat.day 13 hours ago
I think this was experimentally shown by a Youtuber. The speed of sound is a slight oversimplification since there are multiple types (engineeringtoolbox.com/sound-speed-solids-d_713.h…)