RDX
Member
This makes all for an interesting read, and some people have some really entertaining theories, but they leave more questions then answers. I have a question about all of these conspiracy theories: why is it always just a bunch of film makers who arrive at different conclusions? All the detailed reports conducted by scientists using mathematics and physics don’t support the conspiracy theories. The producers find some one who has some credentials (but has done little to no actually research on the matter) and state his thoughts at the time as a fact. They throw out melting points, component strengths, design parameters, etc. But they never do one single calculation based on any of it.
Oh, I guess they do use one equation: Galileo’s law of falling bodies. Even here they have no idea what they are talking about. First of all, this law states that the length that an object falls under the force of gravity is proportional to the time squared. The exact value depends on the physical configuration of the item falling (since we don't live in a vacuum). Most basic free fall experiments are done using spheres. Each piece of the world trade center was unique and had its own drag coefficient/terminal velocity, so to assign a terminal velocity to all the debris is rather stupid. It’s even more stupid to use this equation to assign a terminal or free-fall velocity. The producer of the film is assuming that each piece of debris is a sphere with a fixed diameter and density. The real way of determining an object’s terminal velocity is:
V=((2*m*g)/(ρ*A*C))^.5
Where:
m is the mass of the object falling
g is the acceleration due to gravity
ρ is the density of the material falling through (air)
A is the cross sectional area of the object falling
C is the objects drag coefficient
Anyone want to tell me what the mass of the debris, the density of the material falling and the drag coefficient of the debris was? Now, how long will it take to reach 50% of that terminal velocity? How about 95%? Will it reach 95% of that before it hits the ground. When does the piece of debris in question actually hit the ground? (considering that you can’t see the ground). What will the initial velocity of the projectile have to be in order to make the object fall in just over 10 seconds? Will an initial velocity greater than the terminal velocity result in a fall time that is more than 1 second longer than the fall time at an initial velocity of 0? If so, how high does that intial velocity have to be?
Oh, I guess they do use one equation: Galileo’s law of falling bodies. Even here they have no idea what they are talking about. First of all, this law states that the length that an object falls under the force of gravity is proportional to the time squared. The exact value depends on the physical configuration of the item falling (since we don't live in a vacuum). Most basic free fall experiments are done using spheres. Each piece of the world trade center was unique and had its own drag coefficient/terminal velocity, so to assign a terminal velocity to all the debris is rather stupid. It’s even more stupid to use this equation to assign a terminal or free-fall velocity. The producer of the film is assuming that each piece of debris is a sphere with a fixed diameter and density. The real way of determining an object’s terminal velocity is:
V=((2*m*g)/(ρ*A*C))^.5
Where:
m is the mass of the object falling
g is the acceleration due to gravity
ρ is the density of the material falling through (air)
A is the cross sectional area of the object falling
C is the objects drag coefficient
Anyone want to tell me what the mass of the debris, the density of the material falling and the drag coefficient of the debris was? Now, how long will it take to reach 50% of that terminal velocity? How about 95%? Will it reach 95% of that before it hits the ground. When does the piece of debris in question actually hit the ground? (considering that you can’t see the ground). What will the initial velocity of the projectile have to be in order to make the object fall in just over 10 seconds? Will an initial velocity greater than the terminal velocity result in a fall time that is more than 1 second longer than the fall time at an initial velocity of 0? If so, how high does that intial velocity have to be?
