The Impossible Fast Collapse of The Towers

[Guest]

when you fracture an object into many pieces they do not each carry the same momentum as the original object. lots of little objects do not interact together to produce one large force. they are going to interact with the large object at different points with the large object interacting back seperately on each small object. a collection of pebbles dropped onto a rock of the same mass will not break the rock.

The force is the same regardless of how it is delivered.

You are wrong.

The only thing which can change is the area over which the force is applied, but in this case the debris is largely confined to the same drop zone and so the force is exerted in the same way as if the debris acted as a single object.

Please answer the three questions;

Does a tonne of sand have the same mass as a tonne of rock ?

Where has the mass gone in your scenario ?

Is Mass x velocity a correct definition of momentum and where in that definition does it describe the state of the mass ? Why do you think tidal waves are so distructive since they consist of multiple distinct water molecules.

Br Cornelius

Edited June 8, 2011 by Guest

[jimv]

A hastily made spreadsheet accounting for only conservation of momentum and acceleration due to gravity in the collapse for perusal. I've neglected drag, energy dissipated in fluid compression and the nugatory energy needed to cause failure in each floor's supports. Note all measurements were metric. I had trouble getting such a large pdf to upload to photobucket, so sorry for the ugly text spreadsheet. Cest la vie.

Column 1 is the distance between floors in meters (probably not quite accurate, but close). 2 is the mass of the falling debris in floors applied. So 3 floors is 3, it hits a 4th, it's four, etc. We're assuming the total weight of the top 10 floors can be modeled as 3 floors after initial compression. A fair assumption IMO, but I can put math to this to justify it more accurately. Column 3 is the mass of the falling debris the instant before it impacts the next floor in line. 5 is obviously the acceleration due to gravity. 6 is the velocity of the falling combined mass the instant after impact accounting for conservation of momentum. Column 7 is the time taken in seconds to fall one floor level.

I'll put it in graphs later, but the data is pretty clear. Notice the total time is about 12 seconds, and we made some simplifying assumptions here. The POINT of this is...conservation of momentum does NOT conflict with the actual events.

3 3 7.67 9.8 5.75 0.782

3 4 9.57 9.8 7.66 0.390

3 5 10.89 9.8 9.08 0.330

3 6 11.92 9.8 10.22 0.290

3 7 12.76 9.8 11.17 0.260

3 8 13.52 9.8 12.02 0.240

3 9 14.27 9.8 12.85 0.230

3 10 15 9.8 13.64 0.220

3 11 15.58 9.8 14.28 0.198

3 12 16.2 9.8 14.95 0.196

3 13 16.8 9.8 15.6 0.188

3 14 17.38 9.8 16.22 0.182

3 15 17.94 9.8 16.82 0.175

3 16 18.48 9.8 17.39 0.170

3 17 19.01 9.8 17.96 0.165

3 18 19.52 9.8 18.5 0.160

3 19 20.02 9.8 19.02 0.156

3 20 20.51 9.8 19.54 0.152

3 21 20.99 9.8 20.03 0.148

3 22 21.44 9.8 20.51 0.144

3 23 21.89 9.8 20.98 0.141

3 24 22.33 9.8 21.44 0.138

3 25 22.77 9.8 21.9 0.136

3 26 23.2 9.8 22.34 0.133

3 27 23.62 9.8 22.77 0.130

3 28 24.03 9.8 23.2 0.128

3 29 24.43 9.8 23.62 0.126

3 30 24.83 9.8 24.03 0.124

3 31 25.23 9.8 24.44 0.122

3 32 25.62 9.8 24.84 0.120

3 33 26 9.8 25.23 0.118

3 34 26.37 9.8 25.61 0.116

3 35 26.73 9.8 25.99 0.114

3 36 27.09 9.8 26.35 0.112

3 37 27.44 9.8 26.72 0.111

3 38 27.8 9.8 27.09 0.110

3 39 28.15 9.8 27.45 0.109

3 40 28.5 9.8 27.8 0.107

3 41 28.85 9.8 28.17 0.107

3 42 29.19 9.8 28.52 0.105

3 43 29.52 9.8 28.85 0.103

3 44 29.85 9.8 29.19 0.102

3 45 30.18 9.8 29.52 0.101

3 46 30.5 9.8 29.85 0.100

3 47 30.82 9.8 30.18 0.099

3 48 31.14 9.8 30.51 0.098

3 49 31.46 9.8 30.83 0.097

3 50 31.77 9.8 31.15 0.096

3 51 32.08 9.8 31.46 0.095

3 52 32.38 9.8 31.77 0.094

3 53 32.68 9.8 32.08 0.093

3 54 32.98 9.8 32.38 0.092

3 55 33.27 9.8 32.68 0.091

3 56 33.56 9.8 32.97 0.090

3 57 33.84 9.8 33.26 0.089

3 58 34.12 9.8 33.54 0.088

3 59 34.4 9.8 33.82 0.087

3 60 34.66 9.8 34.1 0.086

3 61 34.94 9.8 34.38 0.086

3 62 35.21 9.8 34.65 0.085

3 63 35.48 9.8 34.93 0.085

3 64 35.75 9.8 35.2 0.084

3 65 36.03 9.8 35.48 0.084

3 66 36.28 9.8 35.74 0.082

3 67 36.54 9.8 36.01 0.082

3 68 36.8 9.8 36.27 0.081

3 69 37.05 9.8 36.52 0.080

3 70 37.31 9.8 36.78 0.080

3 71 37.56 9.8 37.03 0.079

3 72 37.81 9.8 37.29 0.079

3 73 38.05 9.8 37.54 0.078

3 74 38.3 9.8 37.79 0.078

3 75 38.56 9.8 38.05 0.078

3 76 38.81 9.8 38.3 0.077

3 77 39.06 9.8 38.56 0.077

3 78 39.31 9.8 38.81 0.077

3 79 39.56 9.8 39.06 0.076

3 80 39.81 9.8 39.32 0.076

3 81 40.06 9.8 39.57 0.076

3 82 40.31 9.8 39.82 0.075

3 83 40.56 9.8 40.07 0.075

3 84 40.81 9.8 40.33 0.075

3 85 41.05 9.8 40.58 0.074

3 86 41.3 9.8 40.83 0.074

3 87 41.55 9.8 41.08 0.074

3 88 41.8 9.8 41.33 0.073

3 89 42.03 9.8 41.56 0.072

3 90 42.27 9.8 41.81 0.072

3 91 42.5 9.8 42.04 0.071

3 92 42.74 9.8 42.28 0.071

3 93 42.97 9.8 42.51 0.071

3 94 43.2 9.8 42.75 0.070

3 95 43.43 9.8 42.98 0.070

3 96 43.67 9.8 43.22 0.070

3 97 43.89 9.8 43.44 0.069

3 98 44.12 9.8 43.67 0.069

3 99 44.35 9.8 43.91 0.069

3 100 44.57 9.8 44.13 0.068

3 101 44.8 9.8 44.36 0.068

11.994

Edited June 8, 2011 by jimv

[jimv]

The force is the same regardless of how it is delivered.

You are wrong.

The only thing which can change is the area over which the force is applied, but in this case the debris is largely confined to the same drop zone and so the force is exerted in the same way as if the debris acted as a single object.

Please answer the three questions;

Does a tonne of sand have the same mass as a tonne of rock ?

Where has the mass gone in your scenario ?

Is Mass x velocity a correct definition of momentum and where in that definition does it describe the state of the mass ? Why do you think tidal waves are so distructive since they consist of multiple distinct water molecules.

Br Cornelius

Exactly, I think he believes that if the debris is pulverized, it falls as if being poured. But pouring is not the same as falling under the influence of gravity after a systemic failure, because an outside input determines rate of mass flow.

As long as aerodynamic drag is not a factor, the force imparted and change of momentum is unaffected. If you flipped a dump truck full of gravel upside down instantly, the gravel would fall essentially in a clump, and have the same effect as dropping a concrete block of the same dimensions and mass. This is basic modeling.

[Little Fish]

6 is the velocity of the falling combined mass the instant after impact accounting for conservation of momentum

I assume here since you don't describe, that you have calculated velocities after floor impacts using simple momentum equations. the numbers in column 6 (last but one column) look ball park figure correct using simple momentum equations for suspended in air storeys. also the height of a floor is 3.79 meters, not 3.0 meters.

you provide 6 columns of data but refer to 7 columns in your text.

what you have not accounted for is the loss in velocity due to kinetic energy drain during collision which has been calculated as 8.9 times more than the loss of velocity due to conservation of momentum.

factor that into your column 6 (last but one column) and what is your collapse time? I suspect you will have refuted your own argument.

Edited June 9, 2011 by Little Fish

[Guest]

I assume here since you don't describe, that you have calculated velocities after floor impacts using simple momentum equations. the numbers in column 6 (last but one column) look ball park figure correct using simple momentum equations for suspended in air storeys. also the height of a floor is 3.79 meters, not 3.0 meters.

you provide 6 columns of data but refer to 7 columns in your text.

what you have not accounted for is the loss in velocity due to kinetic energy drain during collision which has been calculated as 8.9 times more than the loss of velocity due to conservation of momentum.

factor that into your column 6 (last but one column) and what is your collapse time? I suspect you will have refuted your own argument.

It would seem that that figure has been plucked from thin air to justify a belief that a spontanious collapse could not have taken place. A detailed analysis places the initial loss of energy from kinetic to heat as low as 6.7%, and this figure decreases at each successive impact;

Look to section 4.1 of the following paper for a derivation of this estimate;

http://www.911myths.com/WTCREPORT.pdf

Their conclusions based on their calculations;

 An analysis of the energetics of the WTC collapse events has shown that the kinetic

energy of the aircraft collisions and the subsequent gravitational energy released by the

descending blocks of floors were quite sufficient to destroy the twin towers in the manner

observed. The use of explosive devices in either of the two towers is not necessary to

explain the collapse events and is considered to be highly unlikely.

 The times calculated for the collapse of WTC 1 and WTC 2 show good agreement with

the observed collapse times verifying the basic assumptions of the momentum transfer

model used in the calculations.

 The calculated times represent the minimum theoretical times of building collapse. If

shorter times are to be physically achieved they must involve an unknown additional

source of energy acting in a downward direction. Such a source of energy does not appear

to have been involved in the collapse of the twin towers.

 The kinetic energy of the collapse events was sufficient to crush the WTC floor

concrete in both towers to particles 100 m in diameter, or smaller, which is consistent

with the observed WTC debris particle size distribution.

 From a consideration of the strength of the WTC columns, and the effective area of

support they provided, it is demonstrated that the conditions necessary for the initial floor

collapse were initiated by the aircraft impacts and made irrevocable by the subsequent

eccentric loading of the core columns. The fires that were initiated by the jet fuel spilled

within the towers certainly weakened steel in localized areas in the impact zones.

However, it is suggested that the total collapse of both towers would have occurred even

without the jet fuel fires.

Kinetic energy to heat energy was a small fraction of the overall energy balance and insufficient to retard the momentum driven collapse.

Br Cornelius

[jimv]

I assume here since you don't describe, that you have calculated velocities after floor impacts using simple momentum equations. the numbers in column 6 (last but one column) look ball park figure correct using simple momentum equations for suspended in air storeys. also the height of a floor is 3.79 meters, not 3.0 meters.

you provide 6 columns of data but refer to 7 columns in your text.

what you have not accounted for is the loss in velocity due to kinetic energy drain during collision which has been calculated as 8.9 times more than the loss of velocity due to conservation of momentum.

factor that into your column 6 (last but one column) and what is your collapse time? I suspect you will have refuted your own argument.

Utter nonsense. Kinetic energy lost was lost in the form of heat, you'll find that this amount almost exacly equals the difference in velocities squared time half the impacting mass. And the velocity used to calculate kinetic energy lost in inelastic collisions...is derived from the velocity found from the conservation of momentum equations. To have a different velocity due to kinetic energy drain as opposed to conservation of momentum (which you were big on not long ago) would violate the law of conservation of momentum.

Here's an idea. You wanted numbers. You got numbers. Now why don't you show me where the kinetic energy goes. Give me some numbers of your own devising. Or....admit you're in to a depth so far over your head your ears are popping.

And anytime you make some absurd reference assume you're being held to a real engineer's standards. We have to cite credible sources when we make an assertion, and the do the math to justify our use of said citation. You've been asked over and over and have failed.

[Little Fish]

It would seem that that figure has been plucked from thin air to justify a belief that a spontanious collapse could not have taken place.

that is very unkind.

it has been calculated.

"CALCULATION OF VELOCITY CHANGES DUE TO ENERGY DRAINS DURING THE COLLISION OF THE UPPER AND LOWER BLOCKS"

http://www.journalof911studies.com/volume/2008/TheMissingJolt7.pdf

A detailed analysis places the initial loss of energy from kinetic to heat as low as 6.7%, and this figure decreases at each successive impact;

I never mentioned "heat", neither does the above link.

"We do not consider energy losses due to vibration of the building, heat, and sound, during the initiating impulse, all of which would have required energy from the impulse to produce and thus have an additional effect on velocity loss"

so if we include a further velocity reduction due to generation of heat, then the velocity loss due to collision is actually greater than 8.9 times the velocity loss due to conservation of momentum.

Utter nonsense. Kinetic energy lost was lost in the form of heat, you'll find that this amount almost exacly equals the difference in velocities squared time half the impacting mass

you are saying it takes zero energy to buckle, deform, compress and break all those steel columns?

if the only energy loss is in the form of "heat", then where did the energy come from to break all the columns? I think again you might be in agreement with the "conspiracy theorists".

Edited June 9, 2011 by Little Fish

[Guest]

that is very unkind.

it has been calculated.

"CALCULATION OF VELOCITY CHANGES DUE TO ENERGY DRAINS DURING THE COLLISION OF THE UPPER AND LOWER BLOCKS"

http://www.journalof911studies.com/volume/2008/TheMissingJolt7.pdf

I never mentioned "heat", neither does the above link.

"We do not consider energy losses due to vibration of the building, heat, and sound, during the initiating impulse, all of which would have required energy from the impulse to produce and thus have an additional effect on velocity loss"

so if we include a further velocity reduction due to generation of heat, then the velocity loss due to collision is actually greater than 8.9 times the velocity loss due to conservation of momentum.

you are saying it takes zero energy to buckle, deform, compress and break all those steel columns?

if the only energy loss is in the form of "heat", then where did the energy come from to break all the columns? I think again you might be in agreement with the "conspiracy theorists".

No the paper I linked to and Jimv both explained that this kinetic energy loss ends up as heat - it cannot do otherwise since it is lost and must be conserved as another form of energy - the lowest form of energy is always heat (thermodynamics).

The paper I linked to says the overall loss of kinetic energy - as heat is 6.7% of the system energy and falling thereafter. This could be the 8.9 times the loss due to momentum of redistribution, but what that proves is that that momentum loss (loss of velocity at each impact) is only 0.7% of the overall system energy, and heat loss are both tiny and insignificant in comparison to the increase in linear momentum imparted by gravity.

As for your last statement it shows your utter lack of knowledge of energy - buckling causes heating that is where the energy ends up. Try bending a pieces of metal repeatedly and feeling it after - its hot

Br Cornelius

Edited June 9, 2011 by Guest

[flyingswan]

it has been calculated.

"CALCULATION OF VELOCITY CHANGES DUE TO ENERGY DRAINS DURING THE COLLISION OF THE UPPER AND LOWER BLOCKS"

http://www.journalof911studies.com/volume/2008/TheMissingJolt7.pdf

There are glaring errors in that paper, an obvious problem if you do not have a peer-review process prior to publication.

They use the actual velocity (at less than 1g) after a drop of one floor as the measure of input energy. However, the actual potential energy available corresponds to a 1g acceleration, so a lower velocity means that some of the energy has already gone into deforming the structure.

Secondly, they calculate the energy required to crush the floors above and below the drop and say that this must be instantaneously subtracted from the energy of the upper block to give their reduction in velocity at first impact. However, in reality this energy is only absorbed as the drop continues for those two floors, by which time gravity has continued to act to increase the drop velocity.

They thus have incorrect values for both the amount of energy available and for the change in velocity, hence loss of kinetic energy, at first impact.

[Guest]

It is my contention that there are compelling reasons to suspect that all is not as it seems regarding the twin towers attack, but the actual impact and collapse are not one of them and pursuing this line of inquiry is barking up the wrong tree

Br Cornelius

[jimv]

Spreadsheet adjusted for average floor height of 3.79 meters or approximately 12 feet. Time to ground impact: 13.573 seconds now. Again, we're totally neglecting the minimal mass lost to pulverization that escapes vertical descent due to air compression (the dust you see) and aerodynamic drag, and of course the nugatory time associated with Did you think that adding .79 meters per floor would increase the collapse time by roughly 27%??? Nope. The increased space between floors gives the falling mass more time to accelerate unimpeded without having to transfer momentum. Hence the difference amounted to about 1.6 seconds total. About a 13% difference from my rough dimensions in the original model.

Oh, in the original, I did have a 7th column but didn't copy it. It was a dummy column for outputs of an iterative logic loop to ensure the distance traveled was 3.79 meters (within .02 meters). I used this instead of a quadratic to plug in time intervals that would satisfy the distance equation of motion.

The sheet below shows in 1: mass 2: velocity the instant before impact 3: (duh) 4: velocity after impact 5: Delta V 6: Time between successive impacts 7: Total time elapsed. If you want the iterative column and the code to satisfy some morbid curiosity, I can of course provide them as well.

As for the energy loss due to buckling, shearing, etc...since energy is conserved, as Cornelius mentioned, it becomes heat and acoustic energy (primarily heat of course.)

Edit, just perused the amateur paper linked. The assumption of flow is erroneous first off. Even if flow happened very briefly, and a portion of a lower floor failed, the failure would propagate in short order to catastrophic total failure in extremely short order due to the nature of the supports. The redundancies in velocity calculations are also completely amateurish. As stated earlier...reputable sources. Some kids who clearly haven't made it out of undergrad vs say...scholars from Northwestern, one of the most reputable schools in the nation (who's findings WERE reviewed)...would not be considered credible...ever. Just because it looks good to you, does not mean that it is. That paper looks like my sophomore year lab reports (only I would have obtained the right results.) Yah, I'd bet on the team from Northwestern.

Mass Velocity (initial) m/s g new velocity Velocity Dif time/floor total time

3 8.62 9.8 6.47 2.16 0.880 0.880

4 10.78 9.8 8.62 2.16 0.440 1.320

5 12.19 9.8 10.16 2.03 0.364 1.684

6 13.32 9.8 11.42 1.9 0.323 2.007

7 14.3 9.8 12.51 1.79 0.294 2.301

8 15.2 9.8 13.51 1.69 0.274 2.575

9 16.03 9.8 14.43 1.6 0.257 2.832

10 16.8 9.8 15.27 1.53 0.242 3.074

11 17.53 9.8 16.07 1.46 0.231 3.305

12 18.24 9.8 16.84 1.4 0.221 3.526

13 18.91 9.8 17.56 1.35 0.212 3.738

14 19.56 9.8 18.26 1.3 0.204 3.942

15 20.19 9.8 18.93 1.26 0.197 4.139

16 20.8 9.8 19.58 1.22 0.191 4.330

17 21.39 9.8 20.2 1.19 0.185 4.515

18 21.96 9.8 20.81 1.16 0.180 4.695

19 22.52 9.8 21.4 1.13 0.175 4.870

20 23.07 9.8 21.97 1.1 0.171 5.041

21 23.6 9.8 22.53 1.07 0.166 5.207

22 24.13 9.8 23.08 1.05 0.163 5.370

23 24.63 9.8 23.61 1.03 0.159 5.529

24 25.13 9.8 24.12 1.01 0.155 5.684

25 25.61 9.8 24.63 0.99 0.152 5.836

26 26.1 9.8 25.13 0.97 0.150 5.986

27 26.57 9.8 25.62 0.95 0.147 6.133

28 27.03 9.8 26.1 0.93 0.144 6.277

29 27.48 9.8 26.57 0.92 0.141 6.418

30 27.93 9.8 27.03 0.9 0.139 6.557

31 28.37 9.8 27.48 0.89 0.137 6.694

32 28.81 9.8 27.93 0.87 0.135 6.829

33 29.24 9.8 28.38 0.86 0.133 6.962

34 29.66 9.8 28.81 0.85 0.131 7.093

35 30.08 9.8 29.24 0.84 0.129 7.222

36 30.49 9.8 29.66 0.82 0.127 7.349

37 30.89 9.8 30.08 0.81 0.125 7.474

38 31.29 9.8 30.49 0.8 0.124 7.598

39 31.68 9.8 30.89 0.79 0.122 7.720

40 32.07 9.8 31.29 0.78 0.120 7.840

41 32.45 9.8 31.68 0.77 0.119 7.959

42 32.84 9.8 32.07 0.76 0.118 8.077

43 33.21 9.8 32.45 0.75 0.116 8.193

44 33.58 9.8 32.83 0.75 0.115 8.308

45 33.94 9.8 33.2 0.74 0.113 8.421

46 34.31 9.8 33.58 0.73 0.113 8.534

47 34.67 9.8 33.95 0.72 0.111 8.645

48 35.02 9.8 34.31 0.71 0.110 8.755

49 35.38 9.8 34.67 0.71 0.109 8.864

50 35.73 9.8 35.03 0.7 0.108 8.972

51 36.08 9.8 35.38 0.69 0.107 9.079

52 36.42 9.8 35.74 0.69 0.106 9.185

53 36.75 9.8 36.07 0.68 0.104 9.289

54 37.09 9.8 36.42 0.67 0.104 9.393

55 37.43 9.8 36.76 0.67 0.103 9.496

56 37.76 9.8 37.1 0.66 0.102 9.598

57 38.09 9.8 37.43 0.66 0.101 9.699

58 38.41 9.8 37.76 0.65 0.100 9.799

59 38.73 9.8 38.08 0.65 0.099 9.898

60 39.04 9.8 38.4 0.64 0.098 9.996

61 39.36 9.8 38.73 0.63 0.098 10.094

62 39.68 9.8 39.05 0.63 0.097 10.191

63 39.99 9.8 39.37 0.62 0.096 10.287

64 40.3 9.8 39.68 0.62 0.095 10.382

65 40.61 9.8 39.99 0.62 0.095 10.477

66 40.91 9.8 40.3 0.61 0.094 10.571

67 41.21 9.8 40.61 0.61 0.093 10.664

68 41.51 9.8 40.91 0.6 0.092 10.756

69 41.81 9.8 41.21 0.6 0.092 10.848

70 42.1 9.8 41.51 0.59 0.091 10.939

71 42.39 9.8 41.8 0.59 0.090 11.029

72 42.69 9.8 42.1 0.58 0.090 11.119

73 42.97 9.8 42.39 0.58 0.089 11.208

74 43.27 9.8 42.69 0.58 0.089 11.297

75 43.55 9.8 42.98 0.57 0.088 11.385

76 43.83 9.8 43.26 0.57 0.087 11.472

77 44.11 9.8 43.55 0.57 0.087 11.559

78 44.39 9.8 43.83 0.56 0.086 11.645

79 44.67 9.8 44.11 0.56 0.086 11.731

80 44.95 9.8 44.39 0.55 0.085 11.816

81 45.23 9.8 44.67 0.55 0.085 11.901

82 45.5 9.8 44.95 0.55 0.084 11.985

83 45.77 9.8 45.23 0.54 0.084 12.069

84 46.04 9.8 45.5 0.54 0.083 12.152

85 46.31 9.8 45.77 0.54 0.083 12.235

86 46.58 9.8 46.04 0.54 0.082 12.317

87 46.85 9.8 46.31 0.53 0.082 12.399

88 47.11 9.8 46.58 0.53 0.081 12.480

89 47.37 9.8 46.84 0.53 0.081 12.561

90 47.63 9.8 47.11 0.52 0.080 12.641

91 47.89 9.8 47.37 0.52 0.080 12.721

92 48.14 9.8 47.63 0.52 0.079 12.800

93 48.4 9.8 47.88 0.51 0.079 12.879

94 48.66 9.8 48.15 0.51 0.079 12.958

95 48.91 9.8 48.4 0.51 0.078 13.036

96 49.17 9.8 48.66 0.51 0.078 13.114

97 49.41 9.8 48.91 0.5 0.077 13.191

98 49.66 9.8 49.16 0.5 0.077 13.268

99 49.92 9.8 49.42 0.5 0.077 13.345

100 50.16 9.8 49.67 0.5 0.076 13.421

101 50.41 9.8 49.92 0.49 0.076 13.497

102 50.66 9.8 50.17 0.49 0.076 13.573

Edited June 9, 2011 by jimv

[Little Fish]

The paper I linked to says the overall loss of kinetic energy - as heat is 6.7% of the system energy and falling thereafter. This could be the 8.9 times the loss due to momentum of redistribution, but what that proves is that that momentum loss (loss of velocity at each impact) is only 0.7% of the overall system energy, and heat loss are both tiny and insignificant in comparison to the increase in linear momentum imparted by gravity.

What you are referring to here is not the "overall loss of kinetic energy" but the loss of kinetic energy due to conservation of momentum. check greenings equations, they are just simple momentum equations rearranged in unconventional format, these equations are the same as jimv has used (we have to assume that since he has not revealed his equations). if that is all that is being considered then you are modelling a series of Ali Baba floating slabs/carpets whose magical lift properties disappear at impact.

The loss of kinetic energy due to buckling of columns and beams, deformation etc (App D) is 8.9 times higher than the loss of kinetic energy due to conservation of momentum (App E), as calculated in Appendix D and Appendix E:

http://www.journalof911studies.com/volume/2008/TheMissingJolt7.pdf

To underline the point of your misunderstanding and state in non mathematics terms which you find so confusing, you said this:

"A detailed analysis places the initial loss of energy from kinetic to heat as low as 6.7%, and this figure decreases at each successive impact;"

By claiming that this statement represents the entire kinetic energy loss from the system, you are thus claiming here it requires less energy to destroy the more massive bottom floor than it does the less massive floor near the top.

As for your last statement it shows your utter lack of knowledge of energy - buckling causes heating that is where the energy ends up. Try bending a pieces of metal repeatedly and feeling it after - its hot

I don't know what you think you have demonstrated here, other than your usual caustic brand of ad hominem and preference for adjectives over facts. It matters not where the "energy ends up", what matters is that energy is subtracted from the kinetic energy, which results in a further decrease in velocity (in addition to the velocity loss from conservation of momentum). Edited June 9, 2011 by Little Fish

[Guest]

What you are referring to here is not the "overall loss of kinetic energy" but the loss of kinetic energy due to conservation of momentum. check greenings equations, they are just simple momentum equations rearranged in unconventional format, these equations are the same as jimv has used (we have to assume that since he has not revealed his equations). if that is all that is being considered then you are modelling a series of Ali Baba floating slabs/carpets whose magical lift properties disappear at impact.

The loss of kinetic energy due to buckling of columns and beams, deformation etc (App D) is 8.9 times higher than the loss of kinetic energy due to conservation of momentum (App E), as calculated in Appendix D and Appendix E:

http://www.journalof911studies.com/volume/2008/TheMissingJolt7.pdf

To underline the point of your misunderstanding and state in non mathematics terms which you find so confusing, you said this:

"A detailed analysis places the initial loss of energy from kinetic to heat as low as 6.7%, and this figure decreases at each successive impact;"

By claiming that this statement represents the entire energy loss from the system, you are thus claiming here it requires less energy to destroy the more massive bottom floor than it does the less massive floor near the top.

I don't know what you think you have demonstrated here, other than your usual caustic brand of ad hominem. It matters not where the "energy ends up", what matters is that energy is subtracted from the kinetic energy, which results in a further decrease in velocity (in addition to the velocity loss from conservation of momentum).

What I demonstrated here is that you have no understanding of what energy does when it is transformed - you did not account for what the transformation of energy actually was - kinetic > heat. As such you showed a lack of basic understanding of conservation of energy and of energy transformation. With such a basic lack of understanding I refuse to believe that you actually have the slightest idea what you are talking about.

As to the rest - I will come back to it

One small observation - you are still not seeing that the debris is accumulating with the fall causing both an increase in mass and speed. Your objection that it would take more energy/momentum to crush the lower floors is indeed correct and that is exactly what is happening - both the velocity and mass are increasing and so the momentum is also increasing. If this is not true then where is the missing mass as each floor compounds into the debris load ?

I think the issue with their assumptions is that the structure is acting as a spring load to resist kinetic energy delivered by the fall. I will have to defer to an engineer as to whether this is a valid assumption and whether their estimates are reasonable.

It seems that the initial elastic resistance of the columns had been severely compromised by heat stress due to the fires and so there would have been much reduced elastic resistance to the initial floor drop. Once the initial floor collapse took place gravity driven momentum took over. It also has to be asked, under such a massive load - what was the potential for elastic rebound rather than plastic deformation to take place ?

Br Cornelius

Edited June 9, 2011 by Guest

[The Silver Thong]

You take these guys seriously?

Not really as I just don't believe the official version of events. Even after reading these threads for years I am not convinced of the official report. It does not add up as some seem to think. There is far more to 9/11 IMO.

[Little Fish]

If this is not true then where is the missing mass as each floor compounds into the debris load ?

look at the videos of the collapse, do you observe all the mass accumulating underneath the top block, or do you see something else?

look at pictures of the aftermath, do you observe a square pile of debris fitting the buildings footprint, or do you see something else?

[Guest]

look at the videos of the collapse, do you observe all the mass accumulating underneath the top block, or do you see something else?

look at pictures of the aftermath, do you observe a square pile of debris fitting the buildings footprint, or do you see something else?

The majority remained in the drop zone. The mass reduced to dust was blown out by the compressive air force blast. Dust only represents a small fraction of the overall mass.

Br Cornelius

Edited June 9, 2011 by Guest

[Guest]

Not really as I just don't believe the official version of events. Even after reading these threads for years I am not convinced of the official report. It does not add up as some seem to think. There is far more to 9/11 IMO.

As I said I am inclined to agree with you - but the mechanism for collapse is entirely credible from an engineering point of view and a controlled blast just doesn't account for the actual evidence of a progressive compression from the point of impact (which could not be predicted before the crash).

Br Cornelius

[jimv]

What you are referring to here is not the "overall loss of kinetic energy" but the loss of kinetic energy due to conservation of momentum. check greenings equations, they are just simple momentum equations rearranged in unconventional format, these equations are the same as jimv has used (we have to assume that since he has not revealed his equations)

By claiming that this statement represents the entire kinetic energy loss from the system, you are thus claiming here it requires less energy to destroy the more massive bottom floor than it does the less massive floor near the top.

I don't know what you think you have demonstrated here, other than your usual caustic brand of ad hominem and preference for adjectives over facts. It matters not where the "energy ends up", what matters is that energy is subtracted from the kinetic energy, which results in a further decrease in velocity (in addition to the velocity loss from conservation of momentum).

My math is easy, I mean easy to check for anyone who knows the first thing about engineering. You don't recognize s=s(0)+v(0)*t+1/2*a*t^2?? Or maybe conservation of momentum? If you had the first clue, you could have backwards engineered it in 3 minutes. Time periods, as I stated were found with an iterative loop. The rest is high school physics material. You've been asked to demonstrate at least a shred of real physical and mathematical competency, so that we might see you can at least decipher total bunk amateur engineering and poor modeling from the real deal. You haven't. This is just further testimony to your ineptitude. This is why you're giving us Bob from youtube and two students with a paper that might get a B for effort and a D for results and citing it like it's gospel. Because you don't know enough to know better.

You don't double model a velocity reduction lol. That's why those people are total amateurs. They might be using many of the right equations, but they make the wrong modeling assumptions. The velocity lost between pre and post impact instants in conservation of momentum is noteable, and that's your kinetic energy drop. You don't then take that drop and reverse engineer to find the velocity using balance of kinetic energy and then subtract that velocity as well. It's like saying horse is pushing the cart and the cart is pulling the horse because the horse is pushing it. It's nonsense.

The assumption that buckling took nearly as much energy as posited in the amateur paper. The flanges and brackets and webs supporting lower floors (where anyone who knows structural FMEA would attest) are where failure occurs. Before impact, these serve only to resist the floor's static weight times a small (surprisingly so frankly) FOS. Basically, you could say they balance the floor's moment of inertia. The velocity drop found in the momentum transfer equations is associated with overcoming inertia. (In laymen's vernacular, the energy it takes to get something to move or move faster.) Since the inertia of impacted floors is previously counteracted by the aforementioned supports (duh, otherwise there would be no building at all) it logically follows that the difference in velocity found in the momentum equations when applied to a kinetic energy balance is harmonious with that required to overcome inertia times a factor of safety or cause inelastic failure of support structure (they are one and the same).

The floors on the bottom are not so large at the bottom that they need to be modeled differently, and again, give the points of failure, while some more energy is required to get the job done, you'd say that this bears out using the momentum velocity and new mass changes in a balance of energy equation.

And neglecting heat transfer in support members and successively lowered elastic moduli...yah, that's just wrong too.

Look, as Cornelius suggested, there are other aspects of 9/11 that might be more debatable. I don't buy a bit of it, but its at least more kind to speculation. The science here doesn't lie, and placing explosives in a building so that its collapse is in agreement with sound engineering employed as a result of plane crashes would require a time machine and a team of geniuses. One could argue whether or not these planes were really hijacked by terrorists etc (in my opinion total, complete, disrespectful BS) but you'd have more of a leg to stand on that you do debating science that you don't understand.

[Fanto]

Would people be asking these questions about 911 if Obama had been president during it?

[aquatus1]

Are you kidding? This is the only time engineers have ever had the chance to study the collapse of a skyscraper. It is a goldmine of information! Yes, engineers would have been all over it, regardless of who was the president.

[The Silver Thong]

As I said I am inclined to agree with you - but the mechanism for collapse is entirely credible from an engineering point of view and a controlled blast just doesn't account for the actual evidence of a progressive compression from the point of impact (which could not be predicted before the crash).

Br Cornelius

We do agree on both matters then. The math is over my head however as far as free fall speed goes. I have yet to see to much that contradictes one vs another. Building 7 though still has me wondering.

Edited June 10, 2011 by The Silver Thong

[Fanto]

Are you kidding? This is the only time engineers have ever had the chance to study the collapse of a skyscraper. It is a goldmine of information! Yes, engineers would have been all over it, regardless of who was the president.

But you can't say that the numerically formidable following some of the conspiracy theories behind the collapse have was unaffected by the president during whose term 911 occurred. Many of those who believe in the theories claim "Bush ordered the attacks." Would those same people claim that Obama ordered the attacks?

Engineers can study the collapse with great scrutiny and virulent speculation. That doesn't mean they would necessarily claim Obama ordered the attacks as many claim Bush did.

Also my question was rhetorical, meant to motivate those who read it to question the extent to which Bush's presidency affected the popularity of conspiracy ideas. It may be your opinion that it had little affect, but I think it would be impossible to prove it had no effect. I am not a proponent of the belief that it had a gargantuan effect, I simply find it an interesting angle to consider.

[aquatus1]

Ah, yes, the conspiracy element, one which, I am afraid, I am known for my somewhat skeptical outlook on. I think I am more in line with BrCornelious on this on (shocking, I know), regarding that particular aspect of it; if there is a conspiracy element, evidence for it will not be found in the actual collapse of the towers. Ultimately, conspiracies tend to swivel around political opinions (regardless of whether they are correct or not), and so who the president is would indeed be a high factor. I was thinking in terms of engineering, where science holds reign and presidents can go wave their flags elsewhere (as Former President George Bush was told in polite but no uncertain terms when he proposed to the Academy of Science creating a political board staffed to determine whether it would be advisable to release certain controversial or new scientific discoveries for publication.

But, in all cases, I think we can agree that anyone who wishes to discuss the conspiracy aspects of it need only to create a new thread for it, and there will be many, many, willing participants most eager to share their points of view. Let's keep this thread clear of such distractions, and focus on non-partisan physics.

[Fanto]

Ah, yes, the conspiracy element, one which, I am afraid, I am known for my somewhat skeptical outlook on. I think I am more in line with BrCornelious on this on (shocking, I know), regarding that particular aspect of it; if there is a conspiracy element, evidence for it will not be found in the actual collapse of the towers. Ultimately, conspiracies tend to swivel around political opinions (regardless of whether they are correct or not), and so who the president is would indeed be a high factor. I was thinking in terms of engineering, where science holds reign and presidents can go wave their flags elsewhere (as Former President George Bush was told in polite but no uncertain terms when he proposed to the Academy of Science creating a political board staffed to determine whether it would be advisable to release certain controversial or new scientific discoveries for publication.

But, in all cases, I think we can agree that anyone who wishes to discuss the conspiracy aspects of it need only to create a new thread for it, and there will be many, many, willing participants most eager to share their points of view. Let's keep this thread clear of such distractions, and focus on non-partisan physics.

Definitely agreed.

[Little Fish]

The math is over my head however as far as free fall speed goes. I have yet to see to much that contradictes one vs another.

the calculations presented by jimv are quite simple, although laborious.

for each floor he uses equation of accelerating motion to calculate the time taken to drop from start velocity "u" to velocity "v" just prior to impact into the next floor.

he then adjusts velocity due to momentum considerations, without which he'd end up with absolute freefall.

v= SQUAREROOT[(2 x g x d) + SQUARE(u)]

we know u, start velocity initialy 0

we know g, constant at 9.81

we know d, the distance travelled (distance between floors) as 3.79

so just put the numbers in

so v, the velocity just prior to impact = SQUAREROOT[(2 x 9.81 x 3.79) + 0x0] = 8.62 m/s

this is the velocity of the falling block just prior to impact into the next floor

he then adjusts this velocity for conservation of momentum. you know intuitively that an object hitting another object and coalecsing together as a single mass has to slow, but here is the equation:

M3 x V3 = (m1 x v1) + (m2 x v2)

we want to find V3, the velocity of the coalescing mass after impact. this will account for the velocity reduction due to conservation of momentum, then we can go on to the next floor collision.

for simplicity sake, assume m1 the mass of a floor = 1, and m2 the mass of top block = 12 (12 floors)

v1, the velocity of the floor being impacted is 0

we have calcuated v2 the speed of the top block just prior to impact as 8.62

we know the coalescing mass of M3 = 1 + 12 = 13

so V3 = (0 + 12 x 8.62) / 13 = 7.95 m/s

jimv gets 6.47 (using 9.8 as g, rather than 9.81) because it appears he is modelling the top 3 floors hitting the 106th floor - (0 + 3 x 8.61)/4 = 6.45 m/s, where in reality it was the top 12 floors hitting the 97th floor with the assumption that the floor in between magically vanishes (favouring jimvs position).

so 7.95 m/s goes back into the formula at the top as the initial velocity u, and you repeat the process for each floor collision until you get to the ground, adjusting m2 and M3 to account for which floors are in collison, so the next iteration will be m1=1, m2=13, M3=14.

but...all the above does is model floating floors suspended magically in air, and only works out the velocity loss due to conservation of momentum between floor collisons.

there is another component to velocity loss attributed to the fact the floors were actually supported by rigid columns with a safety factor, that is each story was designed to support many times the weight of the building above it, and in order to break/twist/buckle/deform those supporting columns, a deceleration or jolt, or velocity loss is required.

this jolt is clearly measurable in the verinage demolitions and has been measured, see here:

there was an expected jolt in the verinage demolition.

there was no jolt in the north tower.

if you want to believe that the floors were suspended magically in air or just on the verge of collapse for 30 years, then good luck to you, but I know you are smarter than that.