everyday-lifematerial-science
Steel is an elastic matter and is often used when demonstrating elastic collisions. We also make springs from it.
Due to these properties and for its relative low price, it seems obvious to me to use them to play billiards.
But I don't find any information on the internet about this. Maybe I miss something very obvious?
Please note that the following is all conjectural. I only volunteer it due to the lack of other responses after numerous days, the coolness of the question, and the probably lack of people/references who are explicitly experienced with this specific topic.
As a general relation, I'm sure one can correlate the sound-volume with the total energy being dissipated --- but the noise produced is going to be a (virtually) negligible fraction of that total energy (in general, sound caries very little energy1).
To zeroth order, I think it's safe to assume the waterfall produces white-noise, but obviously that needs to be modified to be more accurate (i.e. probably pink/brown to first order). Also, by considering the transition from a small/gradual slope, to an actual waterfall, I can convince myself that there is definitely dependence on the height of the fall in addition to the water-volume2.
How would height effect the spectrum?
Generally power-spectra exhibit high and low energy power-law (like) cutoffs, and I would expect the same thing in this case. In the low-frequency regime, if you start with a smooth flow before the waterfall, there isn't anything to source perturbations larger than the physical-size scale of the waterfall itself. So, I'd expect a low-energy cutoff at a wavelength comparable to the waterfall height. In other words, the taller the waterfall, the lower the rumble.
There also has to be a high energy cutoff, if for no other reason, to avoid an ultraviolet catastrophe/divergence. But physically, what would cause it? Presumably the smallest scale (highest frequency) perturbations come from flow turbulence3, and thus would be determined primarily by the viscosity and dissipation of the fluid4. Generally such a spectrum falls off like the wavenumber (frequency) to the -5/3 power. But note that this high-frequency cutoff wouldn't seem to change from waterfall to waterfall.
Overall, I'm suggesting (read: conjecturing) the following:
E.g.: The following power spectrum (power vs. frequency - both in arbitrary units).
I'm sure information can be obtained from the sound. In particular, estimates of its height/size, flow-rate, and distance5. I'm also sure this would be quite difficult in practice and, for most purposes, just listening and guessing would probably be as accurate as any quantitative analysis ;)
I suppose its possible waterdrop(let)s could source additional sound at scales comparable to their own size. That would be pretty cool, but I have no idea how to estimate/guess if that's important or not. Probably they would only contribute to sound at wavelengths comparable to their size (and thus constrained by the max/min water-drop sizes6...).
Water, especially in a mist/spray, can be very effective at damping sound (which they used to use for the space-shuttle). I'd assume that this would have a significant effect on the resulting sound for heights/flow-volumes at which a mist/spray is produced.
The acoustic properties of the landscape might also be important, i.e. whether the landscape is open (with the waterfall drop-off being like a step-function) or closed (like the drop-off being at the end of a u-shaped valley, etc).
Finally, the additoinally surfaces involved might be important to consider: e.g. rocks, the surface of the waterfall drop-off, sand near the waterfall base, etc etc.
1: Consider how much sound a 60 Watt amp produces, and assume maybe a 10% efficiency (probably optimistic). That's loud, and carrying a small amount of power compared to what a comparable-loudness waterfall is carrying. The vast-majority of waterfall energy will end up as heat, turbulence, and bulk-motion.
2: I'd also guess that height/volume blend after some saturation point (i.e. 1000 m3/min at 20m height is about the same as 500 m3/min at 40m height)... but lets ignore that for now.
3: Turbulence tends to transfer energy from large-scales to small-scales.
See: http://en.wikipedia.org/wiki/Turbulence
4: Figuring out the actual relation for the smallest size-scale of turbulence is both over my head and, I think, outside the scale of this 'answer'. But it involves things like the Kolmogorov spectrum, and associated length scale.
5: Distance could be estimates based on a combination of the spectrum and volume level - to disentangle the degeneracy between sound-volume and distance.
6: Perhaps the minimum droplet size is determined by it behaving ballistically (instead of forming a mist)?
This is an interesting question, because there is no simple answer - many different things are going on. A quick answer is that many materials don't exhibit clear melting points because heating turns them into something else before they can melt. Here are a couple of examples:
Generally, pure substances have simple, well-defined melting and boiling points. But there are many exceptions. A key example is gypsum - CaSO4 . 2H2O - calcium sulfate dihydrate. When it's heated, it first dehydrates in two steps. Initially it loses 1.5 of the water molecules as vapor, then in a second phase it loses the last 1/2 water molecule as vapor. When this dehydration is complete, the remaining compound is not the compound that we started with - it is now CaSO4. And if heating is continued, much of the CaSO4 will decompose - producing CaO (solid) and SO3 (vapor). Eventually, some melting will be observed, but the melted material will actually be a mixture of CaO and CaSO4.
There's a very detailed description here: http://nvlpubs.nist.gov/nistpubs/jres/27/jresv27n2p191_A1b.pdf
For more complicated materials, similar processes occur, though not always as predictable. Your last question was about wood. As wood heats up it first dries out as you stated - i.e. the free water within the wood boils and leaves as vapor (this is not chemically bound water as in the gypsum). Then as heating continues, the cellulose and other complex organic molecules thermally decompose, producing a lot of light organic compounds such as methane, butane, propane, alcohols, etc. These are essentially small bits of the molecules containing carbon, hydrogen, and oxygen which break off and float away. If oxygen is present, these will burn to produce more heat to speed up the decomposition process, but even without oxygen this decomposition will occur.
Eventually, no more light hydrocarbons can be released, and we are left with carbon and various trace elements including potassium, calcium, magnesium, etc.. This is charcoal. Continued heating can eventually get to the point where these materials melt, but what remains is no longer wood - it's carbon and a few other things - so there is no point at which "wood" will melt.
Best Answer
Q: No Steel balls for billiards.. Maybe I miss something very obvious?
A: Yes Steel balls are way too heavy or they weigh too much ;) in both cases they are way, way too much weight.
The density of steel would result in a much lower speed from conservation of momentum of the cue and momentum of the ball. when driving the ball with a fast cue, a much higher shock to the cue tip would occur causing more injuries to players and cue tips, when impacting a ball of significantly greater mass. So the result would be;