Question for people

[danceboy]

Is thermal mass equal to mass times a (units changing) constant? I.E. is the thermal mass of one 12 kg object equal to that of every other 12 kg object? I've asked a few people who I thought would know (chemical, civil, and mechanical engineers. No, I haven't been able to find a materials scientist.), and all of them said roughly "I think so. I mean, it sounds likely...."

Mind you I've forgotten why I cared in the first place, but care I do.

While we're on the subject of asking random questions; I don't understand what's going on with titanium in hammers and other impact tools (e.g. golf clubs).
I'm guessing that it's just marketing, but they're claiming that a similar sized Ti head will hit harder and be less work to swing. I believe that second part. I even believe that due to KE = 1/2mv^2 a titanium head will have more KE, but I think that inertia is the important thing here (by extrapolation to a dowel with a band of steel wrapped around the end to prevent splitting).

I can also see an advantage to a hammer that doesn't rust, and that doesn't get dinged up if you toss it into your tool box. Further, I think that giving Russia money right now is not a bad thing. I just don't really see a direct advantage for the hand holding the hammer.

Ideas? Comments?

Comments

[herooftheage.livejournal.com]

I don't think that "thermal mass" is a well defined physical term in the way you're looking for. Here's what Wikipedia says:

A thermal mass in the most general term refers to any mass used to absorb and hold heat. Materials with high specific heat like stone, concrete, adobe or water work best.

Specific heats vary for different substances, so in that sense, I'd answer your question as no, thermal masses of two 12 kg. objects are not necessarily the same.

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What I am pretty sure is going on in golf clubs are clever attempts to deliver as much of the force to the ball through the impact zone as possible. Imagine a golf head made out of jello - it doesn't much matter how fast you get the thing moving, too much of the energy gets dissipated in the jello, not the golf ball. If "harder" means "less vibrations", then more of the energy gets spent on the impact.

Now the golf club case is particularly interesting, because the USGA claims designers have figured out how to make materials that rebound out a bit when hit - essentially turning the club face into a spring. I'm not sure I believe it, and the tests I've read about all seem to be tautological - clubs that hit the ball too far are deemed to have "rebound effect." Having looked at the tests, I don't see how they can tell if it is rebound effect of the clubhead, or if clubhead design deforms the ball differently for different heads, or something they haven't thought about. (Golf balls briefly deform on impact, and then go back to their normal shape. Obviously, a bit of energy goes into that deformation.)

The matter is further muddied by the amount of force transferred to the ball not being the only desiderata - how much spin you impart is a lot of the real key. The higher the spin on the ball, the straighter the ball travels, and the farther the effective distance, which is all golfers actually care about.

[danceboy.livejournal.com]

Answer 1 yes, thank you, that was exactly what I was looking for. Now if only I can remember what I was doing that made it matter....

Answer 2, hmm, interesting. I was using much the same analogy at one point, but I didn't think about vibration, just initial deformation, and I know that Ti deforms more than steel on impact so I figured that that would make it worse. That said, I've read that Ti doesn't vibrate as much. It sounds like (and makes sense that) both types of hardness matter to delivering impact.

And it sounds like testing this would be much easier with hammers as spin is gone, angle/technique is easy, and "hardness of thing getting hit" is higher....

As for the studies from the USGA, I remember the FIE (Federation Internationale d'Escrime) using the phrase "kilograms of force" in their rules, and ever after I've tried very hard to ignore sporting organizations using scientific jargon.

Hmm, this means that using Ti for crowbars actually makes a lot of sense as one of the annoying things is that it hurts to hold a crowbar when you hit it with a hammer to get it under a nail.

Thank you very much.