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Question:

How did the planes break the steel?

Maybe it is obvious. But i have thought alot about it.I thought steel at a cool temperature was unbreakable. I am not one for science or physics or engineering (i am a political science major). But i don't understand why the planes that struck the world trade center on 9-11 didn't just dent the side and fall,How did the place break the steel? Was it the velocity? Is steel easily broken?I realized that i wasn't taught how the planes broke the steel, and that no one ever asked. I searched the web and i couldn't find the answer or even anyone who had asked the question before.(i don't care about conspiracy theories, i just want scientific facts)

Answer:

I saw a one-hour program about this on PBS a couple of years ago. The buildings were constructed with the concrete-clad steel supporting columns at the center of the buildings, with a relatively thin lattice of steel struts along the outer wall. When the planes hit, they sheered through the thin steel struts easily by sheer momentum, while, at the same time, the thin steel stripped off the wings. The bodies of the planes got as far as the supporting columns in the center of the buildings, but were stopped there. The heaviest, densest pieces, the engines, went completely through the buildings and popped out the other side. It's important to understand that even light materials can cut through metal, if the light material is going fast enough. I saw this first hand, when I was in the Navy and stationed on board ship. We had a helicopter crash on our flight deck during heavy weather. The blades were made of light, carbon-composite material, but they were going so fast that they cut through the aluminum deck. I still have photos of that damage.
steel is not unbreakable. the world trade centers had a steel infrstructure, but were mostly glass and materials with many other flaws. steel is not the top of the rocwell scale(materials rated by thier hardness) when the planes impacted the outside of the buildings, you have to take into account that the planes skins and infrastructure where made of aluminum(too keep weight down) so once the outer skin of the planes was breached, you have to account for the heat created by burning fuel, friction, and the momentum of a vehicle that weighs tons hitting an immovible object. just keep in mind that if you propel a piece of straw at an proper speed, you can have it impale a full grown palm tree
The buildings only had steel cores within the infrastructure to support the weight and flexibility - quite normal. You would be right if the whole surface of the building was pure reinforced steel with no openings (i.e. a ridiculous giant 100% purely steel tower). Can you imagine the force of a large jet at very high speed hitting a building, along with carrying vast amounts of highly explosive fuel. You don't need to, you've seen it... The bits of steel may well have been undamaged and collectable at ground zero, while the building was destroyed.
1 nothing is unbreakable! 2 it is a question of velocity not that the plane was going very fast but! the difference between an explosion and a detonation is if the flame front is faster or slower than 1000 meter per second If you burn Hydrogen it burns fast, more than 1000 meter per second at that speed a plastic pen like those you use every day will puncture through a steel 2X4 used in modern building walls it is not thick steel but it is still steel! and the plastic piece is hardly deformed Those talking about aviation fuel... this is long, very long after the fact Guru

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