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9/11 Conspiracy Theories - How the Towers Fell
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Quote from CSU1 :I'm pretty sure two planes crashed into the World Trade Center Towers...countless died - that's what happened.

These discussions are dis-tasteful (check the smiley-face dust/rain pic above) - show some respect and leave it alone.

Bravo to you my friend!! I knew a few people who tragically died that day.

I sure as hell don't want to read about it, especially on this forum!!
Quote from tristancliffe :Yes

Seriously? But in this equation KE= 1/2 MV^2, the velocity of the falling dust would be nowhere near the velocity of the solid concrete, right?, therefore the resulting KE would be far less, no?
It's very very strange that a forum about a racing simulator has descended into such a shithole conspiracy theorists hangout, what the **** happened?
It's where I "hangout" anyway, there's a discussion going on about 9/11 so I get involved, what's wrong with that? And! the official theory is just that a theory, and a conspiracy theory at that.

Quote from wildfire083 :Bravo to you my friend!! I knew a few people who tragically died that day.

I sure as hell don't want to read about it, especially on this forum!!

Sorry you feel this way, but if you don't want to read it, you don't have to open the thread, simple.
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(U4IK ST8) DELETED by U4IK ST8
Quote from U4IK ST8 :Seriously? But in this equation KE= 1/2 MV^2, the velocity of the falling dust would be nowhere near the velocity of the solid concrete, right?, therefore the resulting KE would be far less, no?

Why would the dust be slower? Why would the big bits be faster?

And let's clarify that the dust isn't like dust on your coffee table, but much closer to gravel in particle size.
Quote from DeKo :It's very very strange that a forum about a racing simulator has descended into such a shithole conspiracy theorists hangout, what the **** happened?

Exactly!! Or a bunch of trolls/kids with nothing better to do!!
Quote from tristancliffe :Why would the dust be slower? Why would the big bits be faster?

And let's clarify that the dust isn't like dust on your coffee table, but much closer to gravel in particle size.

Yea, ok, I can imagine there would have been gravel sized particles, I hadn't noticed any, but as you can see from videos of the falling debris, the largest pieces of the towers structure are falling faster, maybe because the "dust" isn't going straight down but sideways, or laterally as you might say, so obviously it wouldn't be falling as fast. Of course in an ideal situation everything falls at the force of gravity (heh, just realised you were probably trying to catch me with that one) but in this situation, floors being crushed, core columns and other large pieces of metal falling straight down, the dust wouldn't have the impact it would if it was dropped at the exact time a piece of solid concrete with the same mass was dropped. (is that right? ) It's all coming down separately, not as one mass of gravel or one mass of concrete but spread out so it's impact wouldn't be as it would in an ideal situation, or a controlled enviroment.
Quote from wildfire083 :Bravo to you my friend!! I knew a few people who tragically died that day.

I sure as hell don't want to read about it, especially on this forum!!

Sorry to put it like this, but that's the main advantage of anyone who would mastermind this, rely on emotions and pure shock, that no one dares to question what really happened because it's 'disrespectfull'.
Simply put, it's no difference between perceiving a block of concrete as a 1000 kg heavy mass or as 1 000 000 little pieces, 1 gram each.

`Ek = 0.5 * mass * velocity^2 = 0.5 * 1000* 1^2 = 500 (J)Ek = Ek1 + Ek2 + Ek2 + ... + Ek1000000 = 1000000 * (0.5 * 0,001 * 1^2) = 1000000 * 0.0005 = 500 (J)`

I hope this clears it up...
So who fooled me then to make firm snow balls, i could just grab the snow and throw it at my mates, it would have the same effect?
Fer me personally, anyone with a little common sense know's there is more than meets the eye with the Twin Towers. More evidence for rather than against a conspir. But each to their own. I always find it interesting in the dif points of view's and how they "work it out".

Very little research gives you the info in plain english and the reasons behind why the TT were targeted. When you weight up all the genuine facts, however they fell, anyone would be a little dubious.
I'll be honest, it's tough to get my head around but I'm getting there...

I'm sure I understand the equation for KE. But you guys are only thinking of this in a controlled environment. Like in one hand you have dust or gravel and the other you have a concrete block with the exact same mass, drop them both and they should hit the ground with the same KE, am I right? But at the towers you can clearly see the larger pieces falling faster than the dust, why? Because the dust isn't being dropped exactly like a concrete block would, it's being exploded outward(whether by pancaking floors or explosives, makes no difference in this) and therefore is being dispersed into the air over a larger area which then reduces it's velocity while falling, it wouldn't hit it's highest potential speed before hitting the ground. So in my mind it couldn't possibly have the same or even close to, the same KE as a falling piece of the building.

I'm sure you'll correct me if I'm wrong.
Quote from Boris Lozac :So who fooled me then to make firm snow balls, i could just grab the snow and throw it at my mates, it would have the same effect?

Snow in a snowball is compressed, so it has much less surface/mass ratio which results in much less aero drag. If you did the same experiment in vacuum, there'd be no difference in the amount of kinetic energy the moving mass of snow would transfer to your body regardless of its form...
Quote from MadCatX :Snow in a snowball is compressed, so it has much less surface/mass ratio which results in much less aero drag. If you did the same experiment in vacuum, there'd be no difference in the amount of kinetic energy the moving mass of snow would transfer to your body regardless of its form...

Ok, let me use a different example, if i'd drop my mobile phone on a glass table, and if i blended it in a blender and drop the particles from the same height, in which case would it most likely brake the glass? And why a vacuum, we are talking about simple gravity here.
You're adding new physical phenomenons to the equation.
1) Gazillion of small pieces would fall slower because of the higher overall surface it'd have.
2) Pressure is defined as P = Force/Surface, so the larger the surface, the lower the pressure. If your cell hit a glass with its edge, contact surface would be very small => high pressure => need of a new table. If it hit the glass flat, higher surface and same force mean lower pressure => loud bang, but nothing else.
Kinetic energy E = m v^2
mass doesn't change and in free fall both travel at the same speed.

The term you are looking for is impulse. http://en.wikipedia.org/wiki/Impulse_(physics)

Basically the kinetic energy and impact is the same for a snowball and snowdust if:
- both hit the target at the same speed
- both impacts happen over the same time duration
- both have the same impact area (not really about the impact or kinetic energy but important as how the target sense the impacts. The smaller the area of impact the higher contact pressure for example)

When you try to throw snow dust at someone the dust spreads out and doesn't hit the target at the same time making the impact(s) happen over longer period of time making the impulse smaller. The overall kinetic energy the target recieves is the same though. In the case of dust it just happens over longer period of time over a bigger area.

It's basically like comparing a shotgun to rifle. Except in freefall rifle rounds travel at same speeds as shotgun. Maybe it's more like comparing being thrown small rocks or standing in a sand storm. But of course that's a bit different too if you live in middle east.
Quote from Hyperactive :Kinetic energy E = m v^2
mass doesn't change and in free fall both travel at the same speed. (But KE all depends on what you mention below?)

The term you are looking for is impulse.http://en.wikipedia.org/wiki/Impulse_(physics)

Basically the kinetic energy and impact is the same for a snowball and snowdust if: (Bold is in relation to the dust(gravel sized debris) and large sections of the towers)
- both hit the target at the same speed - This is a possibility
- both impacts happen over the same time duration - Definitely didn't happen. (Smaller debris was spread out therefore took a longer period of time to actually reach the ground)
- both have the same impact area - Definitely not the same impact area (Smaller debris spread out over a wider area) (not really about the impact or kinetic energy but important as how the target sense the impacts. The smaller the area of impact the higher contact pressure for example)

When you try to throw snow dust at someone the dust spreads out and doesn't hit the target at the same time making the impact(s) happen over longer period of time making the impulse smaller. The overall kinetic energy the target recieves is the same though. In the case of dust it just happens over longer period of time over a bigger area.

It's basically like comparing a shotgun to rifle. Except in freefall rifle rounds travel at same speeds as shotgun. Maybe it's more like comparing being thrown small rocks or standing in a sand storm. But of course that's a bit different too if you live in middle east.

So, if the small debris(gravel sized particles) was spread out over a larger area and hit the ground, or structures below, over a longer period of time and the larger debris(large outer sections and core columns of the towers) hit the ground, or structures below, over a shorter period of time, the Impluse of the larger debris would put a greater force on the structures below, therefore doing more damage?

And, they couldn't have the same KE because (a) they both didn't impact over the same period of time (smaller debris=longer time period / larger debris=shorter time period) and (b) they both didn't have the same impact area (smaller debris=larger area / larger debris=smaller area)?

Am I understanding this right?
Quote from U4IK ST8 :So, if the small debris(gravel sized particles) was spread out over a larger area and hit the ground, or structures below, over a longer period of time and the larger debris(large outer sections and core columns of the towers) hit the ground, or structures below, over a shorter period of time, the Impluse of the larger debris would put a greater force on the structures below, therefore doing more damage?

And, they couldn't have the same KE because (a) they both didn't impact over the same period of time (smaller debris=longer time period / larger debris=shorter time period) and (b) they both didn't have the same impact area (smaller debris=larger area / larger debris=smaller area)?

Am I understanding this right?

Kinetic energy is just 0,5 * speed^2 * mass. As the name suggests it is just the total kinetic energy of stuff that is moving. KE has nothing to do with the actual impact nor with the impact area. It is just the total energy the stuff has because it is moving. To get stuff moving from 0 to some speed requires that amount of KE used.

An example: We have 10 000 000 pieces of sand that weight together 20 000kg. So one piece of sand weighs 2 grams. And we have one piece of rock that weighs 20 000kg too. Both are dropped from really long distance so both will get to as fast speed as the aerodynamic drag allows. Which is about the same for both (something around 300kmh).

So kinetic energy for the one big rock KE = 0.5 * 20000 * (300*1000/60/60)^2 = 69,44MJ.
Total kinetic energy is number of rocks * KE of individual pieces = 1 * 69,44MJ = 69,44 MJ.

Kinetic energy for one small sand particle KE = 0.5 * 0,002 * (300*1000/60/60)^2 = 6,944J.
Total kinetic energy is number of rocks * KE of individual pieces = 10 000 000 * 6,944kJ = 69,44 MJ.

Both have the same kinetic energy.

Using KE gives you the total energy. And just that. If you want to calculate the severity of the impact you need to know the time the collision took for example.
Quote from Hyperactive :Kinetic energy is just 0,5 * speed^2 * mass. As the name suggests it is just the total kinetic energy of stuff that is moving. KE has nothing to do with the actual impact nor with the impact area. It is just the total energy the stuff has because it is moving. To get stuff moving from 0 to some speed requires that amount of KE used.

I think I understand the KE = m v^2 equation and what it calculates. I think you lads aren't taking everything into consideration when discussing the KE of the falling debris.
Quote :An example: We have 10 000 000 pieces of sand that weight together 20 000kg. So one piece of sand weighs 2 grams. And we have one piece of rock that weighs 20 000kg too. Both are dropped from really long distance so both will get to as fast speed as the aerodynamic drag allows. Which is about the same for both (something around 300kmh).

So kinetic energy for the one big rock KE = 0.5 * 20000 * (300*1000/60/60)^2 = 69,44MJ.
Total kinetic energy is number of rocks * KE of individual pieces = 1 * 69,44MJ = 69,44 MJ.

Kinetic energy for one small sand particle KE = 0.5 * 0,002 * (300*1000/60/60)^2 = 6,944J.
Total kinetic energy is number of rocks * KE of individual pieces = 10 000 000 * 6,944kJ = 69,44 MJ.

Both have the same kinetic energy.

Obviously they did, because they both reached terminal velocity . Does a grain of sand and a rock have the same aerodynamic drag? Then does a grain of sand and a rock reach terminal velocity if dropped from the same height? I don't think so.
Quote :Using KE gives you the total energy. And just that. If you want to calculate the severity of the impact you need to know the time the collision took for example.

Exactly, you said:
Quote :the kinetic energy and impact is the same for a snowball and snowdust if:
- both hit the target at the same speed
- both impacts happen over the same time duration
- both have the same impact area

So, they[the different sized pieces of debris from the tower] couldn't have the same KE because (a) they both didn't impact over the same period of time (smaller debris covered a larger area so had a longer collision time / larger debris covered a smaller area(in relation to the dust cloud of similar mass) so had a shorter collision time) and (b) they both didn't have the same impact area (smaller debris(dust cloud with a certain mass)=larger area / larger debris(with similar mass)=smaller area(in relation to the dust cloud)). And with different amounts of aerodynamic drag, they both couldn't have reached the same speed falling from the same height.

As you said, to get 10 000 000 grains of sand, weighing 2g per grain, and piece of rock weighing 20 000kg to go "as fast speed as the aerodynamic drag allow", they must be dropped from a really long height, so they reached a speed of "something around 300kmh"! So there's no chance the different sized pieces of the tower reached the same speed just falling from the similar distance as the height of the tower, which was, at the roof top, just 1450 feet (440 m), so the pieces fell roughly 3/4 that distance which is 1 087.5 feet (330m). So they couldn't possibly reach the same speed, which means the velocity wouldn't be the same for the dust particles and the large chunks of the tower, which means the results of the calculation KE = m v^2 would be different.

Now, time to go watch the Monaco GP.
Quote from U4IK ST8 :It seems to me that you were taught different physics to what I understand

this post just gets funnier and funnier with every one of you posts that shows a complete nonunderstanding of really really basic physics
Quote from U4IK ST8 :Obviously they did, because they both reached terminal velocity . Does a grain of sand and a rock have the same aerodynamic drag? Then does a grain of sand and a rock reach terminal velocity if dropped from the same height? I don't think so.
Exactly, you said:
...

Well there's a small lapse on my text there if you read it that closely. Naturally it should say:

the kinetic energy is the same for a snowball and snowdust if:
- both travel at the same speed
- both have same total mass

Impulses are the same if:
- both impacts happen over the same time duration (all the sand particles at the same time too)

If both of those are the same the damage caused by the impact is the same if:
- both have the same impact area
- both have similar rigidity, elasticity, shape and ... you get the point

It's not really about achieving the terminal velocity. Just both having the about same velocity is enough. No one said the KE is precisely 100.0000% the same but close enough to call it same.