The time required to strip off a floor, according to Frank Greening, is a maximum of about 110 milliseconds = 0.110 seconds. It is rather the conservation of momentum that slowed the collapse together with a small additional time for the destruction of each floor.
Below are calculations from a physics blogger…
When I did the calculations, what I got for a thousand feet was about nine seconds- let’s see,
d = 1/2at^2
so
t = (2d/a)^1/2
a is 9.8m/s^2 (acceleration of gravity at Earth’s surface, according to Wikipedia), [He gives this reference so you can double check him.]
d is 417m (height of the World Trade Center towers, same source)
so
t = (834m/9.8m/s^2)^1/2 = 9.23s
OK, so how fast was it going? Easy enough,
v = at
v = (9.8m/s^2 x 9.23s) = 90.4m/s
So in the following second, it would have fallen about another hundred meters. That’s almost a quarter of the height it already fell. And we haven’t even made it to eleven seconds yet; it could have fallen more than twice its height in that additional four seconds. If the top fell freely, in 13.23 seconds it would have fallen about two and one-half times as far as it actually did fall in that time. So the collapse was at much less than free-fall rates.
Let’s see:
KE = 1/2mv^2
The mass of the towers was about 450 million kg, according to this. Four sources, he has. I think that’s pretty definitive. So now we can take the KE of the top floor, and divide by two- that will be the average of the top and bottom floors. Then we’ll compare that to the KE of a floor in the middle, and if they’re comparable, then we’re good to go- take the KE of the top floor and divide by two and multiply by 110 stories. We’ll also assume that the mass is evenly divided among the floors, and that they were loaded to perhaps half of their load rating of 100lbs/sqft. That would be
208ft x 208ft = 43,264sqft
50lbs/sqft * 43264sqft = 2,163,200lbs = 981,211kg
additional weight per floor. So the top floor would be
450,000,000 kg / 110 floors = 4,090,909 kg/floor
so the total mass would be
4,090,909 kg + 981,211 kg = 5,072,120 kg/floor
Now, the velocity at impact we figured above was
90.4m/s
so our
KE = (5,072,120kg x (90.4m/s)^2)/2 = 20,725,088,521J
So, divide by 2 and we get
10,362,544,260J
OK, now let’s try a floor halfway up:
t = (2d/a)^1/2 = (417/9.8)^1/2 = 6.52s
v = at = 9.8*6.52 = 63.93m/s
KE = (mv^2)/2 = (5,072,120kg x (63.93m/s)^2)/2 = 10,363,863,011J
Hey, look at that! They’re almost equal! That means we can just multiply that 10 billion Joules of energy by 110 floors and get the total, to a very good approximation. Let’s see now, that’s
110 floors * 10,362,544,260J (see, I’m being conservative, took the lower value)
= 1,139,879,868,600J
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.
Remember, we haven’t added the energy of four floors of burning wood, plastic, cloth and paper, at- let’s be conservative, say half the weight is stuff like that and half is metal, so 25lbs/sqft? And then how about as much energy as the total collapse again, from the plane impact? And what about the energy from the burning fuel? You know, I’m betting we have a kiloton to play with here. I bet we have a twentieth of the energy that turned the entire city of Nagasaki into a flat burning plain with a hundred-foot hole surrounded by a mile of firestorm to work with. – Schneibster edited by Debunking 911
Let me make this clear, I don’t assume to know what the ACTUAL fall time was. Anyone telling you they know is lying. The above calculation doesn’t say that’s the fall time. That was not its purpose. It’s only a quick calculation which serves its purpose. To show that the buildings could have fallen within the time it did. It’s absurd to suggest one can make simple calculations and know the exact fall time. You need a super computer with weeks of calculation to take into account the office debris, plumbing, ceiling tile etc.. etc… Was it 14 or was it 16? It doesn’t matter to the point I’m making, which is the fall times are well within the possibility for normal collapse. Also, the collapse wasn’t at free fall as conspiracy theorists suggest.
Source: http://www.debunking911.com
Politically Wrong: The details “debunk” the free fall speed “conspiracy theory”. They don’t confirm it!
