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9/11 Physics from Non-Experts

I would have thought seismic readings would be negligible until the first debris hit the ground.

-Gumboot
 
Ok, lets do the math for Yandross for a situation in which each floor is blown sequentially.
If d= distance from the level of initial collapse

it will take 0.78 seconds for the upper section to reach the next floor, 3 meters below initial collapse

and if the next floor is blown at t=0.39 seconds after the initial collapse begins(one half the time for the upper section to reach the next floor)

d=0.5(9.8)t2 for upper section

d= 3 + 0.5(9.8)(t-0.39)2 for the next floor

The upper section mass will meet the floor and columns of the next floor when both of these are equal.

0.5(9.8)t2=3 + 0.5(9.8)(t-0.39)2
4.9t2=3 + 4.9(t-0.39)23=4.9t2 - 4.9(t-0.39)23/4.9 = t2 - (t-0.39)20.612 = t2 - (t-0.39)20.612 = t2 - t2 + 0.78t - 0.152

0.612 = 0.78t - 0.152
t=0.979

Self check:

At 0.979 s the upper section has fallen
d= 0.5(9.8)(0.979)2d= 4.70meters

At t=0.979 the second level has been falling for (0.979-0.39) = 0.589 s
d = 3 + 0.5(9.8)(0.589)2d = 4.70 meters

The upper section has collided with the next level's floor and column mass
The upper section is moving at v=at
v=9.8(0.979) =9.69 m/s

The mass of the second floor is moving at
v=9.8(0.589) = 5.77 m/s

_________________________________________

Now conservation of momentum

Assume that the upper section is 10 times the mass of one floor.

The upper section's momentum at the time it meets the falling mass of the next floor is;
pu=10m(9.69)
whereas the momentum of the next floor's falling mass is
pn=m(5.77)

If they collide inelastically then by conservation of momentum we have
pt=pu + pn
pt=10m(9.69) + m(5.77)

Now we know that pt=11mv where v is the velocity of the now combined masses so;
11mv=10m(9.69) + m(5.77)
11mv=m(96.9 + 5.77)
v=9.33 m/s

The total mass is now slower than the original upper section would have been in an unimpeded free fall.
 
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jaydeehess said:
Ok, lets do the math for Yandross for a situation in which each floor is blown sequentially.
If d= distance from the level of initial collapse

it will take 0.78 seconds for the upper section to reach the next floor, 3 meters below initial collapse

and if the next floor is blown at t=0.39 seconds after the initial collapse begins(one half the time for the upper section to reach the next floor)

d=0.5(9.8)t2 for upper section

d= 3 + 0.5(9.8)(t-0.39)2 for the next floor

The upper section mass will meet the floor and columns of the next floor when both of these are equal.

0.5(9.8)t2=3 + 0.5(9.8)(t-0.39)2
4.9t2=3 + 4.9(t-0.39)23=4.9t2 - 4.9(t-0.39)23/4.9 = t2 - (t-0.39)20.612 = t2 - (t-0.39)20.612 = t2 - t2 + 0.78t - 0.152

0.612 = 0.78t - 0.152
t=0.979

Self check:

At 0.979 s the upper section has fallen
d= 0.5(9.8)(0.979)2d= 4.70meters

At t=0.979 the second level has been falling for (0.979-0.39) = 0.589 s
d = 3 + 0.5(9.8)(0.589)2d = 4.70 meters

The upper section has collided with the next level's floor and column mass
The upper section is moving at v=at
v=9.8(0.979) =9.69 m/s

The mass of the second floor is moving at
v=9.8(0.589) = 5.77 m/s

_________________________________________

Now conservation of momentum

Assume that the upper section is 10 times the mass of one floor.

The upper section's momentum at the time it meets the falling mass of the next floor is;
pu=10m(9.69)
whereas the momentum of the next floor's falling mass is
pn=m(5.77)

If they collide inelastically then by conservation of momentum we have
pt=pu + pn
pt=10m(9.69) + m(5.77)

Now we know that pt=11mv where v is the velocity of the now combined masses so;
11mv=10m(9.69) + m(5.77)
11mv=m(96.9 + 5.77)
v=9.33 m/s

The total mass is now slower than the original upper section would have been in an unimpeded free fall.
Click to expand...
Yandros will not understand this. It is hard for him to think past F=0, and he will F=0 this to death.

It is funny how he does not understand how his sequential explosives theory is slower than "free fall". He will never understand as upper mass destruction of the lower sections of the WTC would be close to free fall time. The WTC on 9/11 was exactly what a gravity collapse of a upper damage failure would look like. Someone could get close to calculating the minimum upper floors required for aircraft impact to sustain global collapse.

Yandros also has problems understanding why the core was not able to handle lateral loads.
 
Ok, this one here apparently comes from a Norwegian truther, and although it may be a case of irony (but honestly, nothing from that camp surprises me anymore), I feel that this one ranks up there with the chicken wire experiments...

4p9g7cg.jpg
 
A flea can jump over 80 times it's own height.

A Norwegian truther can't jump 80 times his own height. Therefore, the Norwegian truther doesn't exist.

Q.E.D.
 
I guess what astonishes me so much about these "common sense" models coming from the Idiot Movement -- milk cartons, rabbit cages, wood, soda cans, eggs duct-taped together, etc. -- isn't the sheer incompetence they represent. Instead, it's the implicit assumption that they've hit on yet another brilliant idea that no engineer in history could have ever conceived.

I don't know about the rest of you guys, but when I was an undergraduate, building models of engineering systems was required coursework. At least it was in the more entertaining classes.

For statics, we built models of rigid, fixed structures. I once built a suspension bridge from toothpicks, wood glue, and sewing thread; it had to span 50 cm, mass under 100 g, and support an ultimate load of at least 25 kg for ten minutes. (My bridge failed at about 120 kg.) So did everybody else in the class. Inspired to look, I see this now goes on all the time.

In physics labs, one builds apparatus that approximate kinetic behavior rather than just the static case. Elastic impact modeled on air tracks, ballistic pendulums and calorimetric dampers for inelastic impacts; we had a playground carrousel for use in building models and testing in a rotating reference frame. The list goes on and on and on.

What the Idiot Movement fails to grasp is that, far from us real scientists neglecting or being unable to come up with such crude models, these are all things we've done perhaps as early as kindergarten. We've moved on, and for good reasons.

There are literally thousands of physics departments in the United States, and few if any of them are exclusively populated with the likes of Steven Jones. Learning more about how to make a good model should not be difficult to do, given one is actually interested in learning rather than just asserting oneself.

Here is a good list of fundamental physics experiments that everyone should at least read about once in their lives. The choices in apparatus for each are highly illuminating, explaining what's important to model in each situation, what isn't, and how.
 
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I am guessing a Pilates Ball could hold up about 500x its weight...so F*(King what.

TAM:)
 
:D Not "funded," we had to supply the toothpicks.

A good engineer is often saddled with lame requirements... it's part of the training!
 
R.Mackey said:
I don't know about the rest of you guys, but when I was an undergraduate, building models of engineering systems was required coursework. At least it was in the more entertaining classes.

For statics, we built models of rigid, fixed structures. I once built a suspension bridge from toothpicks, wood glue, and sewing thread; it had to span 50 cm, mass under 100 g, and support an ultimate load of at least 25 kg for ten minutes. (My bridge failed at about 120 kg.) So did everybody else in the class. Inspired to look, I see this now goes on all the time.
Click to expand...



One of our local Universities used to show this sort of thing on it's local cable distance education channel. I've tried to find it online, but haven't so far. It was nice in that they showed the bridge from the front and from above, and replayed the failures in slo-mo, so you could see exactly how they failed.

I'd like to stick a few twoofers in a room, and make them watch a few years worth of this show, until they understand structure failure.

And in discussing experiments, and how easy it is to get led astray, your link on the physics experiments mentions Cavendish's torsion-bar experiment to measure the gravitational constant. That's one I did as an undergrad, and there's an amusing story about the set-up we used.

When they first started doing this experiment, they had a lot of trouble. Seems no one was getting the correct value for G. As it turns out, they had put the equipment in a long, narrow room, and the door to the room was next to the torsion bar set up. For some reason, they had taken the door off, and the unbalanced mass of the wall opposite the door was throwing off the measurements. They had to go and order an extra-heavy door to balance the gravity of the wall!

Very sensitive setup, that!
 
R.Mackey said:
...I once built a suspension bridge from toothpicks, wood glue, and sewing thread; ...
Click to expand...

Ah, good memories. I had to make mine from popsicle sticks and dental floss. There was the added caviat that the load your suspension bridge had to take was calculated as a function of its weight. So we had to decide whether to make a light bridge to take a small load, or a heavy bridge to take a large load. I chose the former and designed a simple triangle lattice structure. I should have just glued the sticks into a giant brick.

Concerning the video in the original post and the man's lack of understanding the difference between statics and dynamics, he is not alone. I remember watching a video where a group of about five or six people attempted a mass bungee jump from a bridge. It wasn't a bungee "jump", rather they swung from the bridge like a giant pendulum.

The lead daredevil had summed the weights of the people and selected a bungee cord designed to withstand this total. Because Fnet = 0, all should be fine, right? Well, he didn't acount for the dynamic (centripetal) force and the cord broke, resulting in severe injury to some of the people.

I think the pendulum problem is about the first example one learns in studying dynamics. Nevertheless, some people never do.
 
Monza said:
Ah, good memories. I had to make mine from popsicle sticks and dental floss. There was the added caviat that the load your suspension bridge had to take was calculated as a function of its weight. So we had to decide whether to make a light bridge to take a small load, or a heavy bridge to take a large load. I chose the former and designed a simple triangle lattice structure. I should have just glued the sticks into a giant brick.
Click to expand...

Mine was built from those plastic drinking straws that have the bendy end. It proved I had a lot to learn about engineering.
 
R.Mackey said:
I don't know about the rest of you guys, but when I was an undergraduate, building models of engineering systems was required coursework. At least it was in the more entertaining classes.

For statics, we built models of rigid, fixed structures. I once built a suspension bridge from toothpicks, wood glue, and sewing thread; it had to span 50 cm, mass under 100 g, and support an ultimate load of at least 25 kg for ten minutes. (My bridge failed at about 120 kg.) So did everybody else in the class. Inspired to look, I see this now goes on all the time.
Click to expand...

In my Advanced Physics class in high school, we had to construct a simple building out of pasta and glue. We then placed weights on them until they gave out. The hardest part of the whole project was dealing with the minimum and maximum height restrictions, as well as the weight restriction (we may have even had a width/depth restriction, but I don't remember).

Any schmoo could make one of these things out of the thickest pasta they could find, make it an inch tall, and have it hold up to all the weights we had, but that obviously wasn't the point. :)
 
3bodyproblem said:
horatius: I just noticed your tag line from 28th Kingdom, that's priceless
Click to expand...



At the time, I nominated it as the stupidest thing anyone has ever said on the forum, ever. I think it still holds the record, even with "Net force is Zero" Boy.
 
It's the opener of the quote that really cinches it for him. Rather than merely alluding to his genius by comparing himself with the likes of Einstein and Rutherford, he goes right for it. I'll have to go through the first set of emails "Net force=zero" guy sent me to find a nice tag line.
 
Horatius said:
At the time, I nominated it as the stupidest thing anyone has ever said on the forum, ever. I think it still holds the record, even with "Net force is Zero" Boy.
Click to expand...


It was one of those moments of pure beauty.

-Gumboot
 
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