@JakeMarc23 About 9,000 were in the South tower. Out of that about 1,000 died. Most of them evacuated the South tower. The high death toll from both towers are mainly from at or above the impact zone.
@AboundingMyths@LucianoWombato The moment the upper floors started collapsing equilibrium was broken and it was no longer a static system of forces it became a dynamic system.
@AboundingMyths@LucianoWombato The falling floors has momentum and gravity is still pulling the tower down. The collapsing floors are accelerating down to gravity, that and gravity is resulting in enough force that is greater than the normal force produced by the non collapsed floors.