David Chandler jumps the shark

[Grizzly Bear]

Except you got it wrong, because while the first floor may not have been able to "stop" the upper section, it's kinetic energy would be significantly depleted. And the next impact would do even more "stopping" while reducing the kinetic load again.


Sent from our shared looking glass platform

Nope. Wrong. Conservation of momentum kicks in. You dont lose much velocity at all with each of the floor impacts even in the most optimistic case.. The deltaV just with the first impact is -0.54 meters per second (meaning still around 8.09 meters per second as a starting velocity rather than 0) after only the first hit (using the WTC 1 case scenario). So no, theres barely any loss in kinetic energy, and in fact... there is a net gain in potential energy by the time you reach the successive floors since youre calculating for an addition 3.8 meter drop for each additional floor. The math is already part of that

 

[jaydeehess]

Except you got it wrong, because while the first floor may not have been able to "stop" the upper section, it's kinetic energy would be significantly depleted. And the next impact would do even more "stopping" while reducing the kinetic load again.

Wow, just wow. A high school physics student would see the error in that.

Kinetic energy, or momentum , if you choose to work with it that way, both depend on velocity. The initial fall starts from an initial velocity of zero, the gravity accelerates the mass to a higher velocity.
We now move to the second impact as described, and if the first impact did not stop the mass then the velocity at second impact is that remnant velocity PLUS the gain due to gravity through second fall.

PLUS gain in falling mass due to one more level's worth of debris.

Next time consult a physics school teacher.......................or at least one that understands the subject and isn't just teaching the textbook.

 

[GlennB]

Wow, just wow. A high school physics student would see the error in that.

He can't possibly be serious. There he was conceding that the stuff from the first impact only lost some KE and then went on to become part of the second impact.

eta: you edited to say much the same thing

 

[JSanderO]

Wow, just wow. A high school physics student would see the error in that.

Kinetic energy, or momentum , if you choose to work with it that way, both depend on velocity. The initial fall starts from an initial velocity of zero, the gravity accelerates the mass to a higher velocity.
We now move to the second impact as described, and if the first impact did not stop the mass then the velocity at second impact is that remnant velocity PLUS the gain due to gravity through second fall.

PLUS gain in falling mass due to one more level's worth of debris.

Next time consult a physics school teacher.......................or at least one that understands the subject and isn't just teaching the textbook.

why would the impact slow the velocity of the first mass upon impact? It would but it might not very much. How could it not?

 

[GlennB]

why would the impact slow the velocity of the first mass upon impact? It would but it might not very much. How could it not?

Sorry, but I don't understand this at all. What are you asking?

 

[Gamolon]

As I and many others over the years have stated, the upper section cannot destroy more than its own equivalent lower section.

Can you please explain this then?
https://www.youtube.com/watch?v=FCjEi4z2KZA

 

[JSanderO]

Sorry, but I don't understand this at all. What are you asking?

You don't understand?

How bout this... You drop a stone on a horizontal sheet of glass. The stone shatters the glass and continues down until it comes to rest on the ground.

Did the impact and destruction of the glass slow the stone at all? (we know it was not moving at constant velocity because it was dropping)

 

[Grizzly Bear]

He can't possibly be serious. There he was conceding that the stuff from the first impact only lost some KE and then went on to become part of the second impact.

eta: you edited to say much the same thing

Again.... this is a 10+ year old dilemma of treating the towers like completely rigid structures and ignoring localized failure and dynamic loading.

They are treating the net acceleration of the collapse front as a weakening of the structure below rather than a dynamic load force acting on the structure progressively. The error is really; really simplistic

 

[Notconvinced]

By how much?


But the (almost) entire mass of the falling top, increased by the mass of first impacted floor, would be falling under gravity between the first and second impact, which converts potential energy to kinetic energy. Isn't that right? Have you stopped to check if perhaps the kinetic energy added between floor impacts is larger than the kinetic energy lost by the impact?
If no, are you prepared to admit you don't know if the is a net loss of kinetic energy?
If yes - care to show your work and results?

But it's good that you admit the first impact would not bring the kinetic energy to zero.
The kinetic energy arose by the top part descending through the height of one floor, right?
So you already admit that a floor impact dissipates less kinetic energy than is gained by descending through the height of one floor. In other words, the collapse has picked up net kinetic energy by falling and crushing one floor.
This does not reverse on the 2nd floor.
This does not reverse on the 3rd floor.
The falling mass picks up net kinetic energy floor by floor by floor by floor by floor by floor by floor by floor by floor (80+ times).

>So you already admit that a floor impact dissipates less kinetic energy than is gained by descending through the height of one floor.

^i do not admit this. After the first impact, the KE of the falling body is reduced and does not pick up additional mass because that mass is already being carried by the structure below. Then the rapidly decreasing KE of the upper section is no longer sufficient to crush anything and the collapse is arrested.

Mud huts! = toungue in cheek for 2nd/3rd world structures without redundancy, such as readily collapse in earthquakes in Haiti, India, Mexico, etc

Gotta work today, ttyl


Sent from our shared looking glass platform

 

[JSanderO]

^i do not admit this. After the first impact, the KE of the falling body is reduced and does not pick up additional mass because that mass is already being carried by the structure below. Then the rapidly decreasing KE of the upper section is no longer sufficient to crush anything and the collapse is arrested.

Mud huts! = toungue in cheek for 2nd/3rd world structures without redundancy, such as readily collapse in earthquakes in Haiti, India, Mexico, etc

Gotta work today, ttyl

Sent from our shared looking glass platform

WRONG... the falling mass impacts the lower floor and breaks it free from the column and so it is also now falling... more falling mass... then these masses fall on the slab below... break it and then it too begins to fall and so on.

Each impact DOES slow the mass from above a wee bit... but at the same time the "compacted" mass is growing and packs more punch when it falls to the floor below. It's not acting a the sum total of all the mass above... but it's aggregating mass as it "consumes" the next floor down.

 

[beachnut]

>... After the first impact, the KE of the falling body is reduced and does not pick up additional mass because that mass is already being carried by the structure below. Then the rapidly decreasing KE of the upper section is no longer sufficient to crush anything and the collapse is arrested.
...

When the top block hits the lower block at 8.52 m/s, the new mass continues at 7.86 m/s. Not much kinetic energy is expended, in fact we could almost ignore it; because the lower floor can't hold the upper mass.
Floors only hold up themselves, the core and shell hold up each floor, and all the floors.

WWJFKD?

Special 911 truth no math physics, derived by common sense. Do 911 truth follower make this up as they go, or do they copy and paste this from the 911 truth BS book of woo physics?

"Common sense is the collection of prejudices acquired by age eighteen" - Albert Einstein

This is almost as silly as the old "fell in the path of greatest resistance", invoking the secret Truther Law of physics (Newcrapian) where things fall "in the path of least resistance".
The new law applied to avalanches; avalanches stop after the part that started the avalanche reached the equal mass below. The new law, that mass is already being carried by the structure below.
Newcrapian Physics, alive and well at 911 truth, the movement of BS.

 

[GlennB]

How bout this... You drop a stone on a horizontal sheet of glass. The stone shatters the glass and continues down until it comes to rest on the ground.

Did the impact and destruction of the glass slow the stone at all? (we know it was not moving at constant velocity because it was dropping)

Yes, it slowed the stone, of course. The degree of slowing would depend on the stone and the glass. Make it a small stone, small drop and sturdy glass and the glass might not break at all.

The stone had KE represented by ¹/₂mv² , so when the stone fractured the glass some of the KE translated quite quickly into heat. That loss must result in loss of velocity.

 

[lapman]

When the top block hits the lower block at 8.52 m/s, the new mass continues at 7.86 m/s. Not much kinetic energy is expended, in fact we could almost ignore it; because the lower floor can't hold the upper mass.
Floors only hold up themselves, the core and shell hold up each floor, and all the floors.

That's what keeps being ignored by Tony et. al. Once the top section rotated beyond the columns, it could not be supported or stopped. They contend that the floors were a part of the vertical support system, which they weren't.

 

[Dave Rogers]

^i do not admit this. After the first impact, the KE of the falling body is reduced and does not pick up additional mass because that mass is already being carried by the structure below. Then the rapidly decreasing KE of the upper section is no longer sufficient to crush anything and the collapse is arrested.

To use a technical term, bollocks. Most of what the falling mass falls on is air, and once the debris below is disconnected from the structure it's falling too. So the key point you choose to ignore is that the mass of the falling part is continually increasing, and with it its kinetic energy.

Dave

 

[DGM]

^i do not admit this. After the first impact, the KE of the falling body is reduced and does not pick up additional mass because that mass is already being carried by the structure below................

Simple question (actually two). Was that mass in motion prior to impact of the floor above?

Wouldn't you think it needs to be added to the mass above if it wasn't (KE wise)?

 

[jaydeehess]

>So you already admit that a floor impact dissipates less kinetic energy than is gained by descending through the height of one floor.

^i do not admit this. After the first impact, the KE of the falling body is reduced and does not pick up additional mass because that mass is already being carried by the structure below. Then the rapidly decreasing KE of the upper section is no longer sufficient to crush anything and the collapse is arrested.

Mud huts! = toungue in cheek for 2nd/3rd world structures without redundancy, such as readily collapse in earthquakes in Haiti, India, Mexico, etc

Even if you were correct, and it should be bleeding obvious you aren't, the original falling mass is moving faster upon second impact than it was at first impact. Therefore KE and momentum have increased significantly.

If the structure was incapable of arresting first impact how the h is it going to arrest second, obviously greater, impact?

.
You say the KE of falling mass is "rapidly decreasing", but its velocity must be increasing.

Let's say we have a unit mass falling. It hits with velocity v1. It loses half that amount at first impact. At first impact KE was m(v1)². After first impact its velocity is 1/2(v1)
It now falls the same distance as it did to first impact.
It's velocity at second impact is the gain in velocity due to gravity plus the velocity it had retained after first impact, 1.5(v1)
Its KE is m(1.5 *v1)² or 2.25 times its original KE. Fifty percent greater velocity means more than double the KE.


I did this in my head, would have been better if I had a scratch pad. Alas my situation precludes that. I invite corrections.

 

[jaydeehess]

Again.... this is a 10+ year old dilemma of treating the towers like completely rigid structures and ignoring localized failure and dynamic loading.

They are treating the net acceleration of the collapse front as a weakening of the structure below rather than a dynamic load force acting on the structure progressively. The error is really; really simplistic

Both points true.
It wasn't a couple of solid structures, it was a large system of connected structural members connected and arranged to transfer floor loads to the columns, and keep those columns from buckling.

 

[jaydeehess]

To use a technical term, bollocks. Most of what the falling mass falls on is air, and once the debris below is disconnected from the structure it's falling too. So the key point you choose to ignore is that the mass of the falling part is continually increasing, and with it its kinetic energy.

Dave

IMHO, mass is a red herring anyway. KE increases much greater due to increased velocity than by increase in mass.
NT completely ignored that.

 

[DGM]

Even if you were correct, and it should be bleeding obvious you aren't, the original falling mass is moving faster upon second impact than it was at first impact. Therefore KE and momentum have increased significantly.

He's ignoring the fact the mass below is actually subject to gravity and was set in motion and adds to the KE.

You question him on the obvious.................

 

[jaydeehess]

He's ignoring the fact the mass below is actually subject to gravity and was set in motion and adds to the KE.

You question him on the obvious.................

Hah! LOL. True.
Well, while mass increases due to more destroyed structure, its also losing some mass due to shedding off to the sides. Velocity however, of any the blodly H thing that stays within the tower footprint is increasing proportional to 'g', and increasing KE proportional to the square of v. There is a possible argument for steady state mass if shedding equals gain, but there is NO argument that velocity doesn't increase.