Split Thread Was global collapse of WTC inevitable?

[1337m4n]

Fair enough. Now, what happens when you drop both masses?

Then you go to the equations for kinetic energy.

Equation for kinetic energy of loose particulate matter: KE= 1/2 Mass x [Velocity squared]

Equation for kinetic energy of a single solid mass: KE= 1/2 Mass x [Velocity squared]


Amazing! It's almost as if the laws of physics don't care whether a mass is intact or not!

 

[ergo]

Then you go to the equations for kinetic energy.

Equation for kinetic energy of loose particulate matter: KE= 1/2 Mass x [Velocity squared]

Equation for kinetic energy of a single solid mass: KE= 1/2 Mass x [Velocity squared]


Amazing! It's almost as if the laws of physics don't care whether a mass is intact or not!

Hmm. Ok, so:

KE of loose particulate matter= 0.5(.01) x [Velocity squared]
KE of a single solid mass=0.5(10) x [Velocity squared]

 

[kylebisme]

Yeah, you're just confusing kinetic energy with the impact force, as while the former is the same, the latter is less for the particulate matter.

Regardless, consider for a moment how typical controlled demolitions are done, the bottom third or so is blasted out so the upper section can fall far enough to accumulate the force need to crush itself on the ground below. If a section towards the middle is blasted out instead, a larger section would need to be blasted out, since the falling section would have less weight and hence have to fall farther to accumulate the force necessary to crush itself along with the remaining structure below. If a smaller section towards the top weren't blasted out at all, but rather only compromised by impact damage and fires, I doubt global collapse would be inevitable, or even possible for that matter.

 

[ergo]

Yeah, you're just confusing kinetic energy with the impact force, as while the former is the same, the latter is less for the particulate matter.

No, that would be the bee dunkers doing that.

 

[kylebisme]

Yeah, I meant they were trying to get you confused on that, arguing about KE/PE to ignore your point about the difference in impact force.

 

[Furcifer]

I'm honestly not sure whether it's out of ignorance of their definitions and assuming they're the same and outright deceit. We've seen evidence of both so far.

Well he seems to think momentum and work are the same thing.

He doesn't understand static or dynamic loads that's for sure.

He knows that if you throw a handful of flour in someone's face it's different than throwing a handful of rocks. The funny thing is he doesn't have the slightest clue why, he thinks it has something to do with work or some quality he refers to as "impact".

It's well beyond his ability to understand what's going on here but that won't stop him.

 

[GlennB]

never mind

 

[Reactor drone]

Hmm. Ok, so:

KE of loose particulate matter= 0.5(.01) x [Velocity squared]
KE of a single solid mass=0.5(10) x [Velocity squared]

You forgot to multiply by the number of particles.

 

[Newtons Bit]

Yeah, you're just confusing kinetic energy with the impact force, as while the former is the same, the latter is less for the particulate matter.

Regardless, consider for a moment how typical controlled demolitions are done, the bottom third or so is blasted out so the upper section can fall far enough to accumulate the force need to crush itself on the ground below. If a section towards the middle is blasted out instead, a larger section would need to be blasted out, since the falling section would have less weight and hence have to fall farther to accumulate the force necessary to crush itself along with the remaining structure below. If a smaller section towards the top weren't blasted out at all, but rather only compromised by impact damage and fires, I doubt global collapse would be inevitable, or even possible for that matter.

And I've done the energy calculations. So have others. The collapse is inevitable regardless of whether you assume a rigid upper block with perfect axial column strikes or the entire upper block turning into rubble.

 

[beachnut]

Well, since the bee dunkers here know how to calculate the gravitational potential energy of loose particulate matter and compare it to that of a solid object, please go ahead and do so. Show us that there is no difference between the two.

E=mgh

oops, you been bee dunked again. Physics is not your strong suit.

 

[GlennB]

You forgot to multiply by the number of particles.

Yeah. But where he thinks he's taking this line of argument is that the 'particles' of the upper block cannot do enough work against the 'mass' of the lower block owing to their individual low KE.

Quite soon people will have to point out that these particles were impacting not the entire lower block, but components of the lower block. And those components had limited strength at bolts and welds.

i.e. same ol'

 

[ergo]

And I've done the energy calculations. So have others. The collapse is inevitable regardless of whether you assume a rigid upper block with perfect axial column strikes or the entire upper block turning into rubble.

Well, there seems to be plenty of confusion here between kinetic energy and impact force.

 

[Sam.I.Am]

I think that ergo is confusing what he's calling common sense and intuition. His intuition tells him that smaller particles will do less damage. What is apparently counter intuitive for him is that those small particles will have a cumulative effect.

He is comparing the very sudden and sharp dynamic loading of dropping a 10lb anvil a measured distance with the relatively slower dynamic loading of dropping 10 lbs of loose sand from the same distance and saying that the loose sand will do less damage. He's both correct and incorrect. The anvil will do more initial impact damage as the load will be more sudden and concentrated to a smaller area at the first contact. However... in the instance that we are talking about, the collapse of the towers, the collapse progression was due to overloading of bolted connections and that would happen from either an anvil or a pile of loose sand (in this analogy). The sudden shock of an anvil type strike might even cause less overall damage if it penetrated a floor before it could overload the connections.

In other words it doesn't really matter in what form the mass is, liquid, solid or a collection of small particles. It still weighs too much for the floor structure to support it because the floor was never intended or designed to support it. That's why it was inevitable that once the collapse started it wasn't going to stop until it met something that could support the load (in this case the ground).

 

[GlennB]

Well, there seems to be plenty of confusion here between kinetic energy and impact force.

mmmmmmmmmmmmmmmmmmmm ...... nope.

ke=1/2 mv^2
f=ma

Wanna ask about momentum next?

 

[Reactor drone]

Well, there seems to be plenty of confusion here between kinetic energy and impact force.

Let's consider impact force then, F=ma. Since the mass of a broken object and the mass of an intact object is the same, what do you think the difference is between the deceleration rate of a solid object compared to the same mass of particles?

 

[ergo]

mmmmmmmmmmmmmmmmmmmm ...... nope.

f=ma

Okay, so:

impact force of sand particles=.01 x 9.8s²impact force of solid weight=10 x 9.8s²

 

[Reactor drone]

Okay, so:

impact force of sand particles=.01 x 9.8ms^-2impact force of solid weight=10 x 9.8ms^-2

In the interests of accuracy,corrections highlighted.

And you forgot to multiply by the number of particles again.

 

[ergo]

And you forgot to multiply by the number of particles again.

Well, that wouldn't be accurate, as each particle has its own impact on the matter in question, and is subject to friction of its own, so you can't treat the volume of sand particles like an intact object.

 

[twinstead]

Well, that wouldn't be accurate, as each particle has its own impact on the matter in question, and is subject to friction of its own, so you can't treat the volume of sand particles like an intact object.

 

[Gaspode]

Discussion on common sense split to new thread.

Posted By: Gaspode