Split Thread Was global collapse of WTC inevitable?

[Reactor drone]

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.

The calculation above is a static force (in other words you've showed that a smaller mass weighs less than a larger mass), if you had the same mass of small particles on a scale as the mass of a single object they would have the same force (or weight).

So what is the force when 1000 small objects simultaneously hit another object?

It's true that the impact can be spread out more over time giving a lower acceleration and thus lower force but that's significantly effected by particle geometry. A tonne of talcum powder will have less impact than a tonne of bricks which will be very similar to a 1 tonne concrete block.

You seem to want to significantly downplay the impact force of a fractured floor when, in reality, it would be very similar to a whole, intact floor.

 

[Furcifer]

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.

There's no reason for doubt, it's been proven over and over again that the static force of the debris would have overloaded the floors. The dynamic force of the upper section falling was enough to ensure global collapse.

And so the dance continues...

 

[ergo]

The calculation above is a static force (in other words you've showed that a smaller mass weighs less than a larger mass), if you had the same mass of small particles on a scale as the mass of a single object they would have the same force (or weight).

f=ma describes a static force?

So what is the force when 1000 small objects simultaneously hit another object?

I don't know, why don't you calculate it? We know the impact will be different than if they were one large object.

In what circumstance would you have 1000 small objects hitting something simultaneously?

 

[Oystein]

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.

Did you think there IS a difference??

 

[Furcifer]

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.

No it wasn't, only the sand on the outside of the chunk would be subject to friction or drag.

It's usually the simplest of minds that make this mistake. They think because they saw the dust being ejected during the collapse the material inside the cloud was "dust". It wasn't. It was large chunks of structural steel. No "rubble" and not small enough to be subject to drag like a sack of flour thrown off a cliff.

 

[Oystein]

f=ma describes a static force?

Yes. And dynamic force, too. Or simply: Force (mechanical).
Did you think static force has a different formula? Which, pray tell??

I don't know, why don't you calculate it? We know the impact will be different than if they were one large object.

In what circumstance would you have 1000 small objects hitting something simultaneously?

For example, if several cracked and compacted building floors hit another one below.

 

[ergo]

Yes. And dynamic force, too. Or simply: Force (mechanical).
Did you think static force has a different formula? Which, pray tell??

Maybe read some of your colleagues' posts instead of trying to pin all this silliness on me, Oystein.

I seem to recall it was you who suggested there would be little? no? difference between the impact of loose sand and the impact of an anvil on your body.

 

[Reactor drone]

f=ma describes a static force?.

You used the acceleration 9.8ms^-2This is the acceleration an object resting on a surface or in freefall will have due to gravity. It is the acceleration you would use to determine the static force an object exerts.Impact acceleration is likely to be much different.It is determined by how quickly a moving object slows down or comes to rest.

I don't know, why don't you calculate it? We know the impact will be different than if they were one large object.

Do we know that? Do you think 10 x 1kg bricks arranged 1 brick high and released simultaneously will have less impact that a 10kg brick with the same overall dimensions?

In what circumstance would you have 1000 small objects hitting something simultaneously?

1000 small objects would hit simultaneously if they were released simultaneously.

 

[Grizzly Bear]

Ergo really doesn't seem to grasp the idea that the total surface area of contact and the time interval of each "individual impact" as calls it is going to make the difference between getting smacked with 200 one pound sand balls one after the other over 60 minutes versus having 200 of them smack into him in the span of half a second.

Ergo... seriously, consider retaking high school physics... The fact that people have to put in terms of visuals to illustrate the point to you is a really BAD thing

 

[Oystein]

Maybe read some of your colleagues' posts instead of trying to pin all this silliness on me, Oystein.

I seem to recall it was you who suggested there would be little? no? difference between the impact of loose sand and the impact of an anvil on your body.

I quoted your post on potential energy. It appeared like you implied the potential energy for lose objects would be different than for solid objects (assuming equal total mass of course).

You were not talking about impact, and neither were I.

I did not say there would be no difference between the impact of loose sand or an anvil. I said both would break my back. (The anvil would penetrate my skull on top of that, but that is a different matter altogether; my post sought to compare impact of same masses on same area)

 

[beachnut]

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.

You and ergo would rather be hit with one hundred pieces of shot than one large shot from a shot gun. You prefer a big hole, instead of a little hole. I got it; you and ergo can't do physics and have no clue your CD theory is nuts, made up by morons in 911 thruth.

You guys can't do physics and have a some idiotic idea the top section of the WTC was like sand. Good for you guys! After 9 years of idiotic claims is it cool to see new followers, followers, springing up to continue the idiotic claims.

 

[ergo]

Impact acceleration is likely to be much different.It is determined by how quickly a moving object slows down or comes to rest.

You might want to take this up with GlennB, Reactor drone.

So what equation would you use to calculate "impact acceleration"?

Do you think 10 x 1kg bricks arranged 1 brick high and released simultaneously will have less impact that a 10kg brick with the same overall dimensions?

Don't your contortions tire you? We always get these highly detailed, highly conditional scenarios from the bee dunkers.

 

[Reactor drone]

You might want to take this up with GlennB, Reactor drone.

So what equation would you use to calculate "impact acceleration"?



Don't your contortions tire you? We always get these highly detailed, highly conditional scenarios from the bee dunkers.

I'd generally use the equations of motion to determine speed and average acceleration given a known time or distance. Time and distance are harder to determine since different objects and configurations will have different amounts of "give".

In the experiment where you dump a mass of sand on your head the sand uses you as a shock absorber so when it finally hits the ground it has been slowing down for nearly 2 metres. The force you feel on your head will therefore be lower, on average, than the force that the ground would receive were you not there. The peak acceleration may be much higher than the average though so you may still suffer a severly broken neck.

 

[Mr. Skinny]

I realize the JREF is supposed to be an educational resource, but is it really the responsibilty of the JREF forum to teach Physics 101 to people who don't have a basic understanding of the subject?

This really becomes a distraction in a lot of threads. Granted, it's not technically "off topic", but it does seem like a huge waste of time.

Ergo, at least go buy a basic "Physics for Dummies" book, or something like it.

 

[excaza]

You might want to take this up with GlennB, Reactor drone.

So what equation would you use to calculate "impact acceleration"?

What is the acceleration of an object as it hits you? Hint: it's not g.

 

[ergo]

Ergo, at least go buy a basic "Physics for Dummies" book, or something like it.

I might if any of you actually had anything to say, or knew how to say it.

 

[twinstead]

I might if any of you actually had anything to say, or knew how to say it.

So who exactly needs to tell you that you don't "get it" that will make you at least say "hmmmmmm"? Maybe a trip to your local university physics department?

 

[excaza]

I might if any of you actually had anything to say, or knew how to say it.

They're saying it just fine, you're just consistently failing to understand it. And I'm beginning to believe it's intentional.

 

[ergo]

They're saying it just fine, you're just consistently failing to understand it. And I'm beginning to believe it's intentional.

Really, excaza? Dave Rogers thought that potential energy was the critical calculation here. GlennB thinks it's impact force. Reactor drone thinks that the equation for impact force does not describe a dynamic force. He says you need to calculate impact acceleration, but doesn't want to do it.

All we were talking about was the difference in impact force, or ability to do damage, between 1kg of loose sand and a 1kg solid weight.

 

[beachnut]

Really, excaza? Dave Rogers thought that potential energy was the critical calculation here. GlennB thinks it's impact force. Reactor drone thinks that the equation for impact force does not describe a dynamic force. He says you need to calculate impact acceleration, but doesn't want to do it.

All we were talking about was the difference in impact force, or ability to do damage, between 1kg of loose sand and a 1kg solid weight.

You can't do physics so you use your ignorance in physics to make up lies about other people. Cool, you don't have any idea what physics is, as you make up more lies using your failed view of physics as your common sense guide. You make up the dumbest stuff; keep up the failed physics, it make you look very smart, like a 911 truth expert.

The sand is very good to use to cut stuff, the 1kg solid weight would only make a big hole. You have no idea how to do physics and you prove it with every post.

What does sand have to do with the WTC? What does your failed physics have to do with 911? You believe idiotic claims.