on 7/9/08 9:19 pm, Stephen A. Lawrence at [EMAIL PROTECTED] wrote: > > Has anyone here attempted to answer the following three questions? The > first two would involve a little tedious research but are otherwise > straightforward, but the most important -- #3 -- seems hard. > > 1) How much energy is released by ~ 2000 pounds of thermite? (I think > that was the amount discussed.) > > 2) How does that compare with the energy released when the buildings > collapsed? I'd expect that the collapse energy completely dwarfed the > energy that would come from a 1 ton thermite bomb, of course, though I > haven't actually run the numbers, partly because by itself that > comparison doesn't tell us anything; the interesting question here is #3: > > 3) Now, the hard one: A lot of the energy of collapse went into > pulverizing the concrete and breaking or bending steel beams, and some > went into shock waves and assorted other transport mechanisms and was > carried away. However, some undoubtedly also went into *heat* which > remained on site. So, the $64 question is: How much of the energy of > collapse is likely to have turned into heat on-site? > > My guess -- and it is nothing more than a guess -- is that a significant > fraction of the collapse energy *did* turn into heat, and that, in fact, > the amount of heat generated was large enough to melt a significant > amount of steel. But this is just a guess, and I would love to see some > calculations which either confirm or refute it. > > Anybody got such calculations on tap? >
A calculation can be found here near the end of the page: http://www.takeourworldback.com/smokinggun.htm quote: <<As for the kinetic energy available from the massive collapse, this is given by: KE = 0.5mv^2 where v = SQR(2gh) which leads to KE = mgh ...and if all of this was converted to heat and remained within the material, the temperature increase is found by dividing by the mass and heat capacity: T2 - T1 = mgh/(mc) leading to gh/c So for g = 9.807 m/s^2, h = 1368 / 3.2808 m, and c = 450 J/kg.K for steel at around ambient temperature, the mean temperature increase is 9.09 degrees Kelvin. The concrete would be cooler; its specific heat is nearly twice that of steel. This is already a very high estimate for the mean, since that supposes the entire building mass was dropped from 1368 feet. There should be a reducing factor of more than 2, considering the steel was much heavier grade at the bottom, and a considerable amount of the building's mass was below ground. 400,000 tonnes distributed over an area of more than 4,000 square meters averages less than 100 tonnes per square meter. There would not be spots where a few pieces of steel would experience temperature increases that were hundreds of times greater than the mean increase. If a couple of trucks collided head-on, tens of tonnes of mass would be distributed over a cross-section of a few square meters and the impact would be very sharply concentrated over tens of milliseconds as opposed to ten seconds or more. Such collisions do not result in puddles of molten metal on the road. And unfortunately for the "gravitational energy melts steel" theory, even if the steel was already hot, it still requires some 250 KJ/kg for the latent heat of fusion to melt it, which is over 60 times the energy needed to raise from, say, 25 C to 34 C.>>
