Gravity And Free Falling
So you let go another pair of rocks to verify your test results but about halfway down there is a craggy tree jutting out from the canyon wall and one of your rocks hits that limb. It bounces off the limb, loses some velocity then begins to free fall once again. However, the other rock never hit anything and is now far ahead of the rock that hit the limb. It hit the canyon floor in exactly the same amount of time as in the first experiment. Finally, the other rock that hit the limb on the way down hits the ground but it has taken more time then with our first experiment.
The reason is obvious. In order for our experiment on free falling objects to be valid, the objects must be free of any interference on the way down. Otherwise by definition, the object that struck the limb is not in free fall.
I didn't make this stuff up. Newton figured out the formula a long time ago. With his formula you can be at any height, drop any object of any weight (except things like feathers which pose air resistance on the way down slowing their motion) and know exactly how many seconds it will take to reach the earth. If anything interferes, blocks or slows the downward motion of a falling object, it is no longer free falling - period.
So amigos, when rogues tell me that skyscrapers can crash through their steel and reinforced concrete structures in less than ten seconds, which IS mathematically for their heights a free fall rate of speed, I say the rogues are lying. It is physically impossible for a building to pancake through itself in exactly the same amount of time as if it were free falling.
Yet this is what happened and we know of no way to alter physical realities like Newton's Second Law of Motion. So we must figure out how this happened. Therefore, we ask building experts and they all agree. The only way to get a building to drop at free fall speed is to use thermite shape charges that act like a hot knife through butter only with steel. If you pre-plant the explosives in just the right spots on hardened steel support beams, then time their detonation in just the right sequence, a building WILL drop at a free fall speed.
Here is an example of a free falling building that the owner had "pulled down" according to him using pre-laid explosive thermite shape charges.