Eli5: Why did the World Trade Center towers collapse when they were hit so high up?

Question

Was there a design flaw or would any building of that height have failed?

In: Engineering

Answer 1

Things move because of a change in momentum. Remove a single floor, and add the mass of all the other floors above it, then collide it with the remaining building. That’s something like 20,000 metric tons crashing at a speed of 4.9m/s (roughly 11mph).