In
#640:
Props to Grizzly Bear, pgimeno, and ozeco41 for their comments on Szamboti's claims.
Tony Szamboti, what Grizzly Bear was saying about "limiting case studies" is important. You must also consider the scale of physical models being used to study something much larger.
The pressure exerted by beams depends on the size of the structure. As linear size is increased, the footprint increases as the square of the linear expansion, and volume increases as its cube.
So, a quantity like pressure, force per area, at a constant density in the volume, would increase linearly, as pressure = force/area = weight/area = volume*density/area. If density is constant, pressure increases as volume/area = cube(increase)/square(increase) = linearly increasing.
If a man was made twice as big, but with the same density of bones, muscles, and such, the pressure on his leg bones would be twice the normal-sized man's. A ten-times bigger man would have ten times the pressure on bones of similar density and capability; they would be CRUSHED.
Please, do not confuse the behavior of verinage of a building of ten stories or so as indicative of the behavior of a 110-story skyscraper. They are different things.
Look at a spider's legs, then at an elephant's. The elephants legs must be much thicker, relative to body size, to support its weight.
A tiny spider-sized miniature elephant would be much stronger structurally, with less pressure on its bones, than the real elephant.
Now, as for your statement that
This is a
pathetic description of the results I described on Coast-to-Coast, and also posted
here and
here on NMSR.
To determine the velocity loss, I am
USING THE PRINCIPLE OF CONSERVATION OF MOMENTUM.
This is pointed out explicity in my article on momentum. To say that I am "
taking the kinetic energy difference between freefall acceleration and 2/3rds g" is absurd, and shows that you have either(A) not even read my article, (B) read it without a shred of understanding, or (C) intentionally erected a strawman, as you realize the actual model I used isn't as easy a target.
Should you try to perform your own calculations along the lines of my analysis (after reading your comments thus far, I'm not sure you are up to such a task), you would find that the "
2/3rds g" figure is the result of averaging the accelerations for the
FIRST FOUR SECONDS OF TOWER 1'S COLLAPSE.
Over the
last four seconds, however, the short-term acceleration average is only 1/3 g. The short-term averaged acceleration varies for the whole collapse, starting at full g, reducing to 1/3 g at the end. The average over the whole ~12-second collapse is about
0.41g. Again, I point out that these are
averages of periods of true freefall with briefer decelerations from the collisions.
This "2/3g" custard is very ingrained in the truth movement, but is not an
assumption of my calculation, it is a
result of it.
I don't see any need to continue trying to respond to such flagrant strawman arguments. I'm done. I can see why Szamboti's reputation around here is what it is, at least. I hope Chandler can do better.
Dave
