Gravity Can't Do This!

reply to post by -PLB-

Why should these forces have decelerated the mass? On what exactly do you base this?

Newton's third law (the law wmd_2008 claims the matter in the towers was exempt from). Any downwards crushing force is met with an equal and opposite upwards resistance force provided by the lower structure. The reason this should have decelerated the falling mass is that the undamaged lower structure should have been applying an upwards force equal to the capacity of the sum of members being destroyed. This should have been larger than the forces provided by the lower structure pre-collapse, instead it had to be a measly ~1/3rd of that to achieve the accelerations witnessed.

reply to post by wmd_2008

So I take it you will not be re-addressing the post where you claimed in caps that I was wrong but didn't provide a single reason for that statement?

Have a look here at this link

I had a quick look, it seems their main objective is:

This page will show that the collapses were not at freefall, and that there was resistance at every step in the process.

Which does not contradict my claim of ~2/3rds free fall and resistance of ~1/3rd static weight.

If you do not have the ability to directly critique the points I make (this has been going on for several posts now) then I do not trust your ability to provide links of any worthwhile relevance to counter my argument, and as such will no longer be examining the links you provide.

reply to post by wmd_2008

Haven't got time to go through all you post just now

Still no time?

reply to post by WarminIndy


Still harping on about a vacuum? Seriously, either read or think.

"Squibs." Explain.

reply to post by NewAgeMan


They somehow can’t grasp the concept of the inner core holding up one end of the trusses and the exterior columns holding up the other end.
They think there were some other walls in the middle.

The planes were basically flying bombs. And this is what people don't want to accept.

Let's go with the second one.....American Airlines 11 was a Boeing 767.It carries15,982 gallons of fuel. It flew out of Newark, New Jersey, only 8 miles from Manhattan. So it was full of fuel.

Now just understand that this plane with all that fuel hits the building flying at 200 plus miles per hour slams into the tower. As as it hits, not only does the impact cause destruction, but suppose it hits a steel beam that tears a rip in the fuselage, the already burning building now explodes as the entire contents of fuel showers down on the inside of the tower. This now creates a shock wave. When a shock wave is created by high explosives such as TNT (which has a detonation velocity of 6,900 m/s), it will always travel at high, supersonic velocity from its point of origin. So this shock wave is moving at that super sonic velocity travels through the support, and weakens it.

Therefore, because of the shock wave compromise, a vacuum is now created as oxygen is sucked toward the fire, it burns at enormous heat. Each corresponding floor below is filling each lowered floor with fire, in turn pulling more air and making the fire greater and greater as it falls. And we all know that heat may rise, but flammable material does not. That includes the jet fuel that has been flowing into those areas that are lower. We all know that liquids flow downward.

Firemen say that flammable debris was falling even down into the lobby as they were helping people out. Elevators were smoke filled and many were not working any more. It only takes a temperature of 900 degrees to weaken steel. I am sure the temps in the fireball is greater than that. The fireball was following the shock wave, heating an already weakened steel support.

So now, with all of those forces working as it did, is it still not reasonable for a plane to do this?

reply to post by DrinkYourDrug

Any downwards crushing force is met with an equal and opposite upwards resistance force provided by the lower structure.

No one is saying otherwise. But it means nothing when you factor in the huge mass falling.

If I stomp am empty can on the ground yes it will meet my foot with an equal and oposite force. But only up to the structural limit of the can. Which may only be 5-6 lbs. While my foot may contain 50 or more lbs. This can is not going to decelerate my foot by very much.

reply to post by Joey Canoli


Here's another pickup analogy (one that I think better relates to the towers):

-You floor your pickup's throttle and apply just enough brakes to hold it stationary (it's an automatic transmission with the torque converter providing a constant force to the rest of the drive-train).

-Some pesky terrorists crash their pickup into the back of yours and set it in motion. Your pickup begins to accelerate away at 2/3rds of its full throttle, unbraked acceleration capability.

-Could this happen without them also having to sabotage the front brakes (which provide 2/3rds of the vehicle's braking capacity, leaving 1/3rd provided by the rear brakes) at the moment of impact?

reply to post by Joey Canoli

Correct.

How much it should slow down is the issue, and requires an engineering study.

It didn't even remotely slow down when it (should have) made contact with the bottom section.

You believe that every collision should have decelerrated the descending mass. Engineering studies indicate that it should have only resulted in less than freefall acceleration.

Care to cite them?

This is another example of truthers jumpimg the shark - you have demonstrated repeatedly that you have no idea of the difference between deceleration and less than freefall acceleration.

Deceleration- losing acceleration, having a negative acceleration. Less than free-fall acceleration- Any acceleration less than 9.8m/s^2.

*Yawn*

So a little analogy to explain the difference:

1-you floor your pickup's throttle and your pickup will accelerate from 40-80 in 10 seconds. We will equate this with freefall acceleration - nothing holding it back, zero resistance
2- now you floor it again, but drag the brakes lightly the whole time -which applies resistance to the acceleration - and your pickup accelerates from 40-80 in 13 seconds. This lesser acceleration, and using the analogy of #1, is less than freefall acceleration.
3- you floor it again, but at the same time stand on the brakes. Now, instead of accelerating, your pickup loses velocity - 35, 30, 25, 20.... This is deceleration, even though the same amount of yorque is being applied to accelerate the pickup.

Do you understand the difference?

Yes. Now let's use an analogy that's applicable to the collapse twin towers.

1) You're driving in your pickup truck which weighs 2000lbs and you floor it. You smash into a U-Haul truck which weighs 12000lbs. Will your pickup truck slow down? Will your truck, even though it weighs less, exert the same amount of force on the U-haul that it exerts on your truck?

2) Now, instead of a pickup truck, you have box A that weighs 4kg sliding on a frictionless surface. Box A collides with a stationary box B that weights 24kg. Will box A slow down when it makes contact? Will box A exert the same amount of force on box B that box B exerts on box A?

3) Instead of box A sliding on a frictionless surface, box A weighs 4kg and is falling towards the earth. It collides with a stationary box B that weighs 24kg. Will box A slow down when it makes contact? Will the force that box A exerts on box B be the same as the force that box B exerts on box A?

4) Instead of box A weighing 4kg, it weighs 45,000 tons. Box A is falling towards the earth, and it collides with a stationary box B that weights 450,000 tons. Will box A slow down when it makes contact with box B? Will the force that box A exerts on box B be the same as the force that box B exerts on box A?

5) Instead of box A and box B weighing different amounts, let's treat the collapse of the towers as a floor-by-floor interaction rather than two individual chunks colliding. If floor A, the bottom floor of the top section which weighs 4500 tons, collides with a stationary floor B, the top floor of the bottom section which also weighs 4500 tons, will floor A slow down when it makes contact? Will the force exerted on floor B by floor A be the same as the force exerted on floor A by floor B?

Originally posted by samkent
reply to post by DrinkYourDrug

 

Any downwards crushing force is met with an equal and opposite upwards resistance force provided by the lower structure.

No one is saying otherwise. But it means nothing when you factor in the huge mass falling.

If I stomp am empty can on the ground yes it will meet my foot with an equal and oposite force. But only up to the structural limit of the can. Which may only be 5-6 lbs. While my foot may contain 50 or more lbs. This can is not going to decelerate my foot by very much.

Yes, exactly...

en.wikipedia.org...
The yield strength or yield point of a material is defined in engineering and materials science as the stress at which a material begins to deform plastically. Prior to the yield point the material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed some fraction of the deformation will be permanent and non-reversible.
In the three-dimensional space of the principal stresses (σ1,σ2,σ3), an infinite number of yield points form together a yield surface.

Knowledge of the yield point is vital when designing a component since it generally represents an upper limit to the load that can be applied. It is also important for the control of many materials production techniques such as forging, rolling, or pressing. In structural engineering, this is a soft failure mode which does not normally cause catastrophic failure or ultimate failure unless it accelerates buckling.

en.wikipedia.org...

Steel loses strength when heated sufficiently. The critical temperature of a steel member is the temperature at which it cannot safely support its load. Building codes and structural engineering standard practice defines different critical temperatures depending on the structural element type, configuration, orientation, and loading characteristics. The critical temperature is often considered the temperature at which it's yield stress has been reduced to 60% of the room temperature yield stress[3].

So if it loses its strength, then how will it hold the building up?

reply to post by samkent

No one is saying otherwise.

wmd_2008 said otherwise. PLB asked me to explain my reasoning and that statement was a necessary inclusion.

But it means nothing when you factor in the huge mass falling.

Really? Perhaps you want to point out the specific mistakes I made in my post then?

If I stomp am empty can on the ground yes it will meet my foot with an equal and oposite force. But only up to the structural limit of the can. Which may only be 5-6 lbs. While my foot may contain 50 or more lbs. This can is not going to decelerate my foot by very much.

Cool. Crushing cans is fun.

Thanks for agreeing with what I am saying. How about an analogy that relates to the towers though?

reply to post by WarminIndy

So if it loses its strength, then how will it hold the building up?

Lol. Someone's having troubling keeping up with the debate...

reply to post by phantomjack


Your "estimate" of how many fire extinguishers there were in the buildings is waaay off. There were certainly no more than 700 or so. Two or three per floor max.

reply to post by WarminIndy


No, it's not reasonable to conclude planes demolished the buildings, both were designed to survive comparable impacts and fires. And they both did survive, we watched them standing for around an hour each. Then they were demolished in a controlled fashion by pyrotechnic devices and explosives already inside the buildings.

reply to post by samkent


I was referring to the samkent stacked corn and i don't care comment.

reply to post by samkent


What you don't seem to grasp is that there were not only trusses stretching from the cores to the walls but also an abundance of cross trusses, it was a grid of trusses, not just long spans of unsupported trusses, it was all tied together and it was incredibly strong and robust in the face of SIGNIFICANT damage. You can rip out nearly half of it and it'll still be strong enough to hold up everything above it. Less than 10% of supporting columns were damaged and even less than that in terms of damaged trusses. That steel trusswork would have SHREDDED those planes without much damage at all. Learn some physics, and quit mouthing off about # in ignorance, clearly you don't know how the towers were constructed or how they were demolished.

Originally posted by samkent
reply to post by DrinkYourDrug

 

Any downwards crushing force is met with an equal and opposite upwards resistance force provided by the lower structure.

No one is saying otherwise. But it means nothing when you factor in the huge mass falling.

If I stomp am empty can on the ground yes it will meet my foot with an equal and oposite force. But only up to the structural limit of the can. Which may only be 5-6 lbs. While my foot may contain 50 or more lbs. This can is not going to decelerate my foot by very much.

But what would happen with 10 cans stacked on top of each other.

The first can would slow your foot down. The second can would slow it more, etc., etc.

And then there is the fact that cans weigh less than your foot. The masses need to be proportional to show the effect of the conservation of momentum. So why hasn't an experiment been done to show a collapse was possible? If it was.



psik

Originally posted by WarminIndy
So if it loses its strength, then how will it hold the building up?

There's one thing you OSers keep missing, well more than one actually but, even IF all the columns, and trusses, failed you still have floors, concrete and steel pans, that are going to stack up and slow the collapse. 15 floors can not crush 95 floors, no matter how you try to spin it.

Even IF your 15 floors could crush the 95 where did the 15 floors go? If they had the energy to crush more floors than themselves, and stay in one piece (they would have to to crush anything), then where did they go?

In reality though those 15 floors would have to be crushed themselves IF they could crush floors bellow them, equal opposite reaction. Even if you use the back assward thinking of OSer and pretend it was 15 floors falling on one floor, the one floor will react with the first floor falling on it, and the only thing keeping the extra mass of the 15 floors effecting the one floor is the trusses. The only thing keeping the impacted floor from failing is the SAME trusses. So if you want to think the 15 floors dropping caused the trusses to fail on the impacted floor, then you have to realize that the trusses of the first floor of the dropping block will also fail, as the forces pushing up are the same as the forces pushing down on the two impacting floors. But in reality there is more force pushing up than down, and to claim only the impacted floor would fail, and not also the impacting floor is incorrect reasoning. You can not ignore the mass of the lower structure that the top is dropping on. That reasoning leads to an incorrect conclusion that favours collapse.

Originally posted by DrinkYourDrug

Here's another pickup analogy (one that I think better relates to the towers):

-You floor your pickup's throttle and apply just enough brakes to hold it stationary (it's an automatic transmission with the torque converter providing a constant force to the rest of the drive-train).

Ok, this would represent the towers and the resistance given to collapse by the columns.

-Some pesky terrorists crash their pickup into the back of yours and set it in motion. Your pickup begins to accelerate away at 2/3rds of its full throttle, unbraked acceleration capability.

Fail.

Nothing crashed onto the the top of the towers to set them in motion and overcome the resistance of the brakes/columns.

-Could this happen without them also having to sabotage the front brakes (which provide 2/3rds of the vehicle's braking capacity, leaving 1/3rd provided by the rear brakes) at the moment of impact?

Sorry, but your ana;ogy fails.

try again.

Originally posted by TupacShakur

It didn't even remotely slow down when it (should have) made contact with the bottom section.

Your making a quantitative claim here. To refer back yo my analogy, you are claiming that the barakes are applied fully/there was enough resistance to achieve deceleration, rather than less than freefall acceleration.

You have provided zero maths to help your claim. This makes your claim a bare assertion and thus can be discarded until you provide those quantitative maths.

I won't be holding my breath...

] Deceleration- losing acceleration, having a negative acceleration. Less than free-fall acceleration- Any acceleration less than 9.8m/s^2.

So you can cite the difference, yet have no idea how to back your claim with maths? Astonishingly arrogant to believe that you are right then.

1) You're driving in your pickup truck which weighs 2000lbs and you floor it. You smash into a U-Haul truck which weighs 12000lbs. Will your pickup truck slow down? Will your truck, even though it weighs less, exert the same amount of force on the U-haul that it exerts on your truck?

My 2000 lb pickup/ upper 15 stories didn't smash into a 12,00 lb truck/95 stories. My 2000 lb pickup smashed into a 100 lb moped/single floor.

So your analogy is flawed and useless to understand the mechanics of the collapse.

2) Now, instead of a pickup truck, you have box A that weighs 4kg sliding on a frictionless surface. Box A collides with a stationary box B that weights 24kg. Will box A slow down when it makes contact? Will box A exert the same amount of force on box B that box B exerts on box A?

Yes and yes.

3) Instead of box A sliding on a frictionless surface, box A weighs 4kg and is falling towards the earth. It collides with a stationary box B that weighs 24kg. Will box A slow down when it makes contact? Will the force that box A exerts on box B be the same as the force that box B exerts on box A?

In reality, the 4 kg box/upper 15 stories didn't collide with a 24kg box/95 stories. The 4 kg box collided with a .2 kg box/ 1 floor.

4) Instead of box A weighing 4kg, it weighs 45,000 tons. Box A is falling towards the earth, and it collides with a stationary box B that weights 450,000 tons. Will box A slow down when it makes contact with box B? Will the force that box A exerts on box B be the same as the force that box B exerts on box A?

You're making the same mistake. 45k tons didn't collide with the whole tower at the same instant. Only with one floor.

5) Instead of box A and box B weighing different amounts, let's treat the collapse of the towers as a floor-by-floor interaction rather than two individual chunks colliding. If floor A, the bottom floor of the top section which weighs 4500 tons, collides with a stationary floor B, the top floor of the bottom section which also weighs 4500 tons, will floor A slow down when it makes contact? Will the force exerted on floor B by floor A be the same as the force exerted on floor A by floor B?

This didn't happen either.

The entire 15 story section -floors AND columns - moved as a unit onto the upper floor of B, destroying it and turning it into rubble, along with the lower floor of A. The floors can't stop this momentum, and so they failed.

Your understanding of the dynamics of what must have happened is pathetic.

The floors were destroyed one at a time, all the way to the ground.

Originally posted by ANOK

IF all the columns, and trusses, failed you still have floors, concrete and steel pans, that are going to stack up and slow the collapse.

More stupidity.

The only way they can stack up is if they are failing, which also means they are in motion, which mean that there is increasing ke/momentum.

15 floors can not crush 95 floors, no matter how you try to spin it.

Good thing that this is just a truther strawman then, cuz no rational person is saying that.

The entire 15 story upper part fell as a unit onto one floor and destroyed it. Then it fell through air to the next floor and destroyed that one.

The 95 floors were destroyed one at a time.

Even IF your 15 floors could crush the 95 where did the 15 floors go? If they had the energy to crush more floors than themselves, and stay in one piece (they would have to to crush anything), then where did they go?

they were destroyed into pieces during the 1000' fall to the ground/churning maelstrom of debris.

Did you expect to see them intact? Pure stupid to think or claim so.

In reality though those 15 floors would have to be crushed themselves

Agreed. They would be nearly unrecognizable junk.

IF they could crush floors bellow them, equal opposite reaction.

There is no doubt among the sane that they could.

Even if you use the back assward thinking of OSer and pretend it was 15 floors falling on one floor

the sane world agrees with "OSers".

the one floor will react with the first floor falling on it,

Don't forget the columns......

and the only thing keeping the extra mass of the 15 floors effecting the one floor is the trusses.

Pure stupidity.

The only thing keeping the impacted floor from failing is the SAME trusses.

And the connections to the columns.

So if you want to think the 15 floors dropping caused the trusses to fail on the impacted floor, then you have to realize that the trusses of the first floor of the dropping block will also fail, as the forces pushing up are the same as the forces pushing down on the two impacting floors.

You're forgetting the columns again.

But in reality there is more force pushing up than down

And now, the equal and opposite forces get thrown out the window to satisfy cognitive dissonance.

and to claim only the impacted floor would fail, and not also the impacting floor is incorrect reasoning.

The sane realize that the dropping floor will be junked as well.

You can not ignore the mass of the lower structure that the top is dropping on. That reasoning leads to an incorrect conclusion that favours collapse.

15 stories were in motion. They impacted only one floor.

keep on trolling truther lies though....

reply to post by Joey Canoli

Fail.

Nothing crashed onto the the top of the towers to set them in motion and overcome the resistance of the brakes/columns.

Of course not. That aspect of my analogy represented a simplification of the events leading to initiation of collapse and top section being set in motion. It is an analogy after all...

Sorry, but your ana;ogy fails.

try again.

Actually guy, it is your analogy that fails. The amount of brake pressure applied needs some reference pressure where pre some event the force of "gravity" is counteracted and completely balanced.

Try again plox, and try not to be so ironic with your fail cries. I guess civilized debate is above your intellectual capacity and this is what I should expect from an emotional responder?


reply to post by Joey Canoli

More stupidity.

they are in motion, which mean that there is increasing ke/momentum.

Don't worry about a constant or decreasing velocity.

Originally posted by DrinkYourDrug
Newton's third law (the law wmd_2008 claims the matter in the towers was exempt from). Any downwards crushing force is met with an equal and opposite upwards resistance force provided by the lower structure. The reason this should have decelerated the falling mass is that the undamaged lower structure should have been applying an upwards force equal to the capacity of the sum of members being destroyed. This should have been larger than the forces provided by the lower structure pre-collapse (1), instead it had to be a measly ~1/3rd (2) of that to achieve the accelerations witnessed.

You have been deceived on two accounts (I numbered them in your quoted text).

1) The lower floors that had to endure most of the falling mass were not designed to hold up the mass of the top section. The load capacity of the floors was much lower than the columns.

2) This 1/3gm figure is the average force. That means that momentarily or locally the force could have exceeded the maximal load capacity, only long enough to make the member fail, while from that moment on moment there was no resistance anymore at all. If 1/9 of a second the force was 3gm, and 8/9 it was 0gm, the average force is 1/3gm. (note that this is just an example).

Originally posted by ANOK

Originally posted by WarminIndy
So if it loses its strength, then how will it hold the building up?

There's one thing you OSers keep missing, well more than one actually but, even IF all the columns, and trusses, failed you still have floors, concrete and steel pans, that are going to stack up and slow the collapse. 15 floors can not crush 95 floors, no matter how you try to spin it.

Even IF your 15 floors could crush the 95 where did the 15 floors go? If they had the energy to crush more floors than themselves, and stay in one piece (they would have to to crush anything), then where did they go?

In reality though those 15 floors would have to be crushed themselves IF they could crush floors bellow them, equal opposite reaction. Even if you use the back assward thinking of OSer and pretend it was 15 floors falling on one floor, the one floor will react with the first floor falling on it, and the only thing keeping the extra mass of the 15 floors effecting the one floor is the trusses. The only thing keeping the impacted floor from failing is the SAME trusses. So if you want to think the 15 floors dropping caused the trusses to fail on the impacted floor, then you have to realize that the trusses of the first floor of the dropping block will also fail, as the forces pushing up are the same as the forces pushing down on the two impacting floors. But in reality there is more force pushing up than down, and to claim only the impacted floor would fail, and not also the impacting floor is incorrect reasoning. You can not ignore the mass of the lower structure that the top is dropping on. That reasoning leads to an incorrect conclusion that favours collapse.

What he said.