Back to high-school: today, physics 101

My friend L. has just emailed me this video, which I new about, but which I do want to post here for those of you who say that they are not engineers and that they have a hard time coming to a conclusion about what happened with WTC7.  In this video David Chandler, a high-school physics teacher, uses basic (high-school level) yet absolutely incontrovertible laws of physics to prove tat