Crash Physics: Deceleration & Material Properties

[shure]

The force is equal and opposite so it would be the same as if the building was moving and the plane was stationary. The speed doesn't matter, the stronger denser object will always prevail. Except, as we see, in the case of 9/11 where basic laws were defied!

 

[xxChrisxx]

Oh dear, you are talking total rubbish and don't seem to be realising it. The statements you make are correct, but you clearly don't understand the physics of the situation.The same object can have different 'effective strengths' depending on how its loaded. You cannot assert that object a is more dense than than object b so object b will survive better, as that does not hold true in all situations. Concrete is a perfect example of this, its compressive strength is very impressive, but it lacks tensile strength. It is also not a tough material and tends to fracture easily. This is the reason why concrete walls don't stand up well to bending and impact loads, and is the reason why steel reenforcement is used.

The walls of thw WTC were designed to withstand hurricane force winds up to , which impart much more force on the building that a plane does, so by your logic the building should have survived no problem. The difference is this load is distributed and not localised.

You also state the speed does not matter, this is also untrue. Dynamic loading is tricky business, but a simplified way of looking at it is the faster the impact (more correctly the greater the acceleration/deceleration of the object) the more localised the damage will be as the material doesn't have time to react and distribute the load.

The statement that it doesn't matter if its the building or the plane that's considered to be moving is true. The thing that matters is HOW the plane hits the building and the deceleration of the plane determines the forces involved. The total damage will depends on the KE at impact.The basic laws of physics were not broken in the case of the plane impacts.

 

[shure]

Both the mass and the tensile strength of the tower are greater than that of the plane. There is to argue with someone who argues that airplanes can meld into steel and concrete building.

Your not fooling me so you must be trying to fool yourself, clearly you can't know what your talking about with responses like you have made!

 

[Twinbee]

shure, might it have something to do with how the shape of the plane is very long, so there's lot of metal behind each 'last bit' to keep on 'puncturing' the building's outside as it comes up against it? It would be like a needle against cheese.

So instead of 0.25" of plane against say 1" of building, it's the entire length of plane (1000s" against 1" of building).

 

[shure]

Are you comparing the plane and the WTC to a neelde and cheese? Thats funny!

You must be familiar with the bug hitting a windshield question?

The bug would be the plane and the windshield would be the WTC. There is no way the bug would penetrate the windshield!

 

[xxChrisxx]

Shure

Buy books,
Read books,
Learn.

That is all.Until you rise above your crass lack of knowledge on this subject, there is little 'arguement' to be had regarding this.

 

[shure]

Ha, ha, you need to follow your own advice "xxChrisxx" since you seem to think a Boeing 767 can juts meld into a steel and concrete tower!

 

[xxChrisxx]

The evidence shows that quite clearly a plane can penetrate the steel and concrete wall of a building.

'I don't think so' and 'I don't believe that can happen' is not a valid argument to the contrary, no matter how often you say it.As opposed to this pointless discourse, let me ask you a question for my own amusement.

What do you think happened to the planes and building at impact, and why?

 

[shure]

Evidence! You mean the video shows that a plane can penetrate a STEEL and CONCRETE building.

FACTS dictate that water freezes at 32°F. Facts also dictate that what we are seeing in the video is unrealistic.

With your logic I can say I can fly because I saw a video of Superman!

 

[xxChrisxx]

Its dissapointing that the thread has gone in such a poor direction, with very little reasoned response from you. The crash was described using real physical principles, based on dynamic loading, crash geometry and the way materials behave. You have decided that 'no it doesn't is a better arguemnt'

What a shame.

 

[shure]

Your right "xxChrisxx" you have taken this thread in a poor direction from your first post. The nonsense you come up with to justify what we are seeing in the video is astounding.

 

[slider142]

What do ad hominem attacks have to do with crash physics? This thread needs to be closed.

 

[alibongo]

What do ad hominem attacks have to do with crash physics? This thread needs to be closed.

Please don't close the thread, I came here for answers and haven't had a decent explanation yet.

 

[alibongo]

This thread is conerning the 1st imapct, which takes place roughly perpendicular to the outer wall of the building.

This thread is not concerning the first impact, where did you get that idea xxChrisxx?
Hookes Law has already pointed out it's not relevant to compare a simulation of the first impact with a video of the second impact.

To clarify, this thread is about the alleged video footage showing the second impact.

 

[alibongo]

The main thing that confuses me about the impact is why the wings weren't ripped off, I would have expected this to happen due to the distributed load along the wing gausing a large moment at the wing/fuselage joint.

I agree with you xxChrisxx, this is most confusing. You're keen on simulations, look at the sim for the Pentagon hit. The wings fold back and break off at impact.

Shure posted some very relevant points, but you resorted to insults, like you did when I posted relevant questions.

It seems you're trying to invent a theory to fit the event shown in the videos.

Why don't the wings break off in the vids I posted xxChrisxx?

 

[Doc Al]

Enough already. Closed pending moderation.

 

[russ_watters]

Sorry, folks, but 9/11 conspiracy theory threads are not allowed here. This thread slipped by us or it would have been locked sooner. Here's the problem with such threads:

It seems you're trying to invent a theory to fit the event shown in the videos.

Well good, because that's how science works! You take evidence and try to explain the evidence in terms of known physical theory. But I see that you never did approach this thread that way - you posted a youtube link to a 9/11 video clip and called it a fake. See, the problem here is that the 9/11 conspiracy theorists have simply chosen to believe that the evidence is not evidence and as a result are not looking for an explanation of that evidence, but only a confirmation of their preconfirmed opinion. That's not scientific, but it is the reason why these threads go in circles to nowhere.

The issues here really aren't that difficult if one choses to investigate them with an open mind. Start by reading the [real] scientific reports on the subject. I like to help those with open minds, so if you pm me with truly honest/open minded questions, I'll answer them. But the thread stays locked.

[edit]
I'll give you one tidbit that may help here though:

shouldn't 500,000 tons of steel slow down the plane?

That's an improperly asked question because it assumes that the building did not slow down the plane - it did. What you may really mean is 'shouldn't the building slow the plane to a stop, with part of the plane intact, outside the building' (like in the simulation where the tail never gets to the building). The answer is no, but not because of the strength of the building, but because of the strength of the plane. The plane is nowhere near strong enough to keep itself together at impact. If it hit an impenetrable wall, it would simply fold up like an accordion and break apart as it did - every bit of the aluminum structure would be pulverized. Now that isn't what happened, but the point is that there is no no impact scenario under which any part of a plane could slow to a stop, intact. Parts of it can punch through with little deceleration and other parts could disintegrate on impact, but since the video doesn't show what is happening inside the building, it is difficult to see which is happening to what.