Can a collapsing building melt steel
The [Heat of Fusion heat of fusion] for steel is 272,000 joules per kilogram. MassAndPeWtc.pdf
The [Specific Heat specific heat] of iron is about the same as the specific heat of steel. It increases with temperature, reaching a value of about 0.72 Joules per gram at 1400 degrees C. MassAndPeWtc.pdf
The in-service mass of Tower 1 (North Tower) of the World Trade is found to be 288,100 metric tons (317,500 short tons). The gravitational potential energy above the 1st floor is found to be 480,600 MJ (133,500 kWh). MassAndPeWtc.pdf
The total weight of structural steel in the each WTC tower is approximently 90,718 metric tons (100,000 short tons). MassAndPeWtc.pdf
1 ton of TNT is 4.184E9 J or 4184 MJ
The gravitational potential energy of WTC1 is equivalent to 114 tonnes to TNT. MassAndPeWtc.pdf
The gravitational potential energy of 1 kg of steel at the top of WTC1 (1368 ft or 407m) is 1*9.8*407 = 3989 J
The energy required to change steel from solid at 800C (1472F) to liquid is about 750,400 joules per kilogram. journalof911studies.com
The addidtional 746411 J necessary to melt a 800C 1kg piece of steel is not available in a fire.
Energy is conserved. As each mass was lifted into the towers it acquired gravitational potential energy equal to E=Mgh where M is the mass of the object, g is the acceleration of gravity and h is the height above the ground. When an object falls it's gravational potential energy is converted into kinetic energy of the form 1/2Mv^2. In a single body system, like a ball being dropped, when mass M hits the ground it will have converted ALL of it's gravational potential energy into kinetic energy. In a multi body system such as the demolition of the Twin Towers some of the gravatioal potential energy is also converted into heat via friction between the falling bodies, slowing them some.
This heat can raise the temperature of materials. The energy required to change steel from solid at 800C to liquid is 750,400 J/kg (journalof911studies.com) , if ALL of the gravational potential energy of WTC1 was converted into heat it could change 640,458 kg (706 short tons) of steel from solid to liquid. Assuming all of the gravational potential energy is converted to heat is absurd as no energy would be left to turn to kinetic energy. In reality only a small fraction of a % of gravational potential energy can be converted to heat in a falling body.
according to tests conducted by NIST, no WTC steel samples saw temperatures of 600 C, which is well below the melting point of steel. (6)
This is the amount of energy required to raise a unit mass of a substance, one degree. For example at room temperature the specific heat of iron is 0.45 joules per gram per degree Centigrade. (7) The temperature has to be specified since the specific heat varies with temperature. The specific heat of iron is about the same as the specific heat of steel. It increases with temperature, reaching a value of about 0.72 Joules per gram at 1400 degrees C. (8)