Hijacked commercial airliners were purposely crashed into them.
The forces acting upon the twin towers were primarily gravity, wind loads, and the impact of the airplanes on 9/11. These forces caused structural damage and ultimately led to the collapse of the towers.
No, it was actually the heat from the fires that weakened the steel in the structures. The resulting "pancake" collapse was a result of the same thing that happens when you knock over a row of dominoes - the failure of the floor where the planes hit (due to the above weakened steel supports) caused it to fall directly down on the floor below, which could not withstand such an impact, and it failed, hitting the floor below, etc.
The twin towers collapsed on September 11, 2001, after being struck by hijacked airplanes. The impact of the planes and subsequent fires weakened the buildings' structures, leading to their ultimate collapse.
The collapse of the Twin Towers on September 11, 2001, was caused by the impact of two hijacked planes (American Airlines Flight 11 and United Airlines Flight 175) crashing into the buildings, which weakened the structures, combined with the intense heat from the resulting fires that caused the steel framework to lose its structural integrity.
The Twin Towers were destroyed in a terrorist attack on September 11, 2001. Two hijacked airplanes were intentionally flown into the buildings, causing them to collapse. The attacks resulted in the deaths of nearly 3,000 people.
The Twin Towers did not fall down in the traditional sense. They were broken up at least in part by explosions and the resulting debris fell down. http://www.youtube.com/watch?v=nUDoGuLpirc
The terrorist group called Al Qaeda
2 planes with terrorists wanted to destroy the twin towers
Tuesday.
They weren't even built in the 1700s, so no. They crashed in 2001
2001
tuesday
well osama wanted to knock down the twin towers because he wanted to get pay back
quickly
the twin towers fall
Iraq did not knock down the Twin Towers
peeps knocked it down