Here's the math, that Pulsar already linked to in the PFI section:
http://www.debunking911.com/freefall.htm
http://www.debunking911.com/freefall.htm
Now that's not specifically for TWC7, but you can do the same calculations for WTC7 and understand that basically a building this size collapsing is like a small, vertical nuclear weapon once it gets started.OK, now how much is 1.1 trillion joules in tons of TNT-equivalent? Let's see, now, a ton of TNT is 4,184,000,000J. So how many tons of TNT is 1,139,879,868,600J?
1,139,879,868,600J / 4,184,000,000J/t = 272t
Now, that's 272 tons of TNT, more or less; five hundred forty one-thousand-pound blockbuster bombs, more or less. That's over a quarter kiloton. We're talking about as much energy as a small nuclear weapon- and we've only calculated the kinetic energy of the falling building. We haven't added in the burning fuel, or the burning paper and cloth and wood and plastic, or the kinetic energy of impact of the plane (which, by the way, would have substantially turned to heat, and been put into the tower by the plane debris, that's another small nuclear weapon-equivalent) and we've got enough heat to melt the entire whole thing.