Geddes on Waveguides

[dlr]

Originally posted by MJL21193

Lets reiterate: Water can be slightly compressed, but it takes incredible force to do so. Sound waves do not have enough energy to do this. They do have enough energy to make the molecules move, as demonstrated above, this takes very little force.

You've said nothing that is not explained fully by the equations that define the velocity of sound in a liquid. That velocity is dependent in part on the compressibility. It does not matter how large or small that factor. It is not a question of a simplistic and faulty mental model that cannot be explained. Yours is simply a faulty mental model and your explanation of the physics is wrong.

Dave

[MEH]

And off topic.

This is "Geddes on Waveguides"; please start another thread called "John on the Compressibility of Water" that we can more easily ignore.

[MJL21193]

Originally posted by dlr


You've said nothing that is not explained fully by the equations that define the velocity of sound in a liquid. That velocity is dependent in part on the compressibility. It does not matter how large or small that factor. It is not a question of a simplistic and faulty mental model that cannot be explained. Yours is simply a faulty mental model and your explanation of the physics is wrong.

Dave

Here goes:
Velocity of sound in a liquid is governed by density. At a given pressure, water is most dense at 0*C- it's melting point. Don't forget about temperature when you talk about density. Temperature will have an impact on density, as the temp goes up, the molecule move faster and the water expands. All the way up to 100*C where water will boil and change states to a gas. This is a 1600 times volume expansion from liquid to gaseous.
So, we go from nearly no molecular movement at 0*C to 1600 times that at 100*C and at not point along this change can you compress it, without changing temperature. Yes, I said you cannot compress steam without a temperature change, and as water is at higher density at a lower temperature, you need to make the temperature drop to increase density.
So, in order for your sound wave to compress water, it needs to lower it's temperature. This is easily accomplished at the bottom of the ocean, from the trillions of pounds of pressure the mass of water is exerting, but up here on the crust, under normal room temperatures, with the amount of energy available in a sound wave, this will not happen.

Read about steam engines.

[gedlee]

Please move this pointless discussion somewhere else.

[y8s]

I hear the oceans are going to rise because of global warming. that sounds like sea level compressibility.