New guy here: Questions for official hypothesis

[uk_dave]

So long as there was enough distance between the boards to allow gravity to accelerate the ball and overcome the minimal deceleration caused when it hit the styrofoam board.

With no space between the boards the ball would stop (unless it had already fallen from a great height)

ETA - It's also a poor analogy because the broken styrofoam is adding very little to the mass falling on the lower boards

 

[Myriad]

About the bowling ball.

Let ask this question then.

Is it possible to stop a bowling ball falling through Styrofoam boards by adding more boards?

Or will that ball continue to fall, as long as it can pass through the first board.

Weight and density, etc can be adjusted to anything as long as the bowling ball can break the first board.

It depends on the details.

For each styrofoam board the bowling ball falls through, two things happen: the ball is slowed by the board, and the ball is accelerated by gravity. In energy terms, you can say the ball expends (loses) kinetic energy by straining and breaking the styrofoam, and gains kinetic energy from the conversion of potential energy as it falls.

Once you know what happens for the first board, you can predict the rest. But you need to observe more than just whether or not the first board breaks. You need to consider the speed the ball is falling. Especially, whether it is moving slower or faster the moment it meets the second board, than the moment it met the first board.

If the ball has slowed down, then it was more slowed by the board than it was sped up by gravity (that is, if it loses more kinetic energy to the board than it gains from the potential energy converted to kinetic energy in falling that distance), and it could eventually slow to a stop. Whether or not it does so before it gets all the way to the ground depends on how much it's slowed, how fast it was going in the first place, and how many boards there are. if it does reach the ground, then making the stack sufficiently higher would prevent it from doing so.

If the ball is going faster after the first board (that is, it gains more kinetic energy from converted potential energy than it expended on the board), then it will not stop no matter how high the stack of boards is. In that case making the structure taller by adding more boards could not change the outcome.

Changing the spacing of the boards could affect the outcome, though, because that changes the ratio of energy required to break a board versus potential energy converted by falling the distance of one board-to-board space. Changing the thickness or strength of the boards would also change that ratio.

Respectfully,
Myriad

 

[Sizzler]

It depends on the details.

For each styrofoam board the bowling ball falls through, two things happen: the ball is slowed by the board, and the ball is accelerated by gravity. In energy terms, you can say the ball expends (loses) kinetic energy by straining and breaking the styrofoam, and gains kinetic energy from the conversion of potential energy as it falls.

Once you know what happens for the first board, you can predict the rest. But you need to observe more than just whether or not the first board breaks. You need to consider the speed the ball is falling. Especially, whether it is moving slower or faster the moment it meets the second board, than the moment it met the first board.

If the ball has slowed down, then it was more slowed by the board than it was sped up by gravity (that is, if it loses more kinetic energy to the board than it gains from the potential energy converted to kinetic energy in falling that distance), and it could eventually slow to a stop. Whether or not it does so before it gets all the way to the ground depends on how much it's slowed, how fast it was going in the first place, and how many boards there are. if it does reach the ground, then making the stack sufficiently higher would prevent it from doing so.

If the ball is going faster after the first board (that is, it gains more kinetic energy from converted potential energy than it expended on the board), then it will not stop no matter how high the stack of boards is. In that case making the structure taller by adding more boards could not change the outcome.

Changing the spacing of the boards could affect the outcome, though, because that changes the ratio of energy required to break a board versus potential energy converted by falling the distance of one board-to-board space. Changing the thickness or strength of the boards would also change that ratio.

Respectfully,
Myriad

Great! Thanks for that.

One problem though.

You wrote:

If the ball has slowed down, then it was more slowed by the board than it was sped up by gravity (that is, if it loses more kinetic energy to the board than it gains from the potential energy converted to kinetic energy in falling that distance), and it could eventually slow to a stop. Whether or not it does so before it gets all the way to the ground depends on how much it's slowed, how fast it was going in the first place, and how many boards there are. if it does reach the ground, then making the stack sufficiently higher would prevent it from doing so.

If the ball looses more energy going through the board than is gained by gravity, but still breaks the board and falls to the next, wouldn't it still have the same amount of energy needed to break the next board, no matter how many boards there are?

As long as the initial drop of 2 feet is enough to break the board, and all other boards are 2 feet a part, shouldn't they all continue to break even if the ball slows down when breaking through each board?

 

[Sizzler]

I found a paper that describes the issue I have with progressive collapse times of 15 seconds.

I can't post links yet so I will post a quote from Jones' paper where he cites the paper I am talking about.

When you go through the calculation, which Ken Kuttler did, it takes a lot longer just because of conservation of momentum and energy. Ken’s calculations show numbers over 25 seconds for the complete collapse of Tower 1.26 That is a lot longer than free fall, and longer than the observed destruction of either Tower. If you add into the calculation a reasonable safety factor, Kuttler then concludes that WTC 1 would not have continued to complete collapse at all. This result agrees with Gordon Ross who says the initial collapse will actually STOP.24 There will be damage, of course, but the support columns will flex and absorb the kinetic energy of the upper block of floors. Plus you have concrete breaking and pulverization going on which removes kinetic energy from the system. And as he looks at conservation of energy and momentum he finds that the destruction actually stops, the collapse is arrested, and it doesn’t go to complete collapse

Kuttler paper is this one:

Estimates for time to collapse of WTC1

can be found at journal of 9-11 studies.

I am of course skeptical of this paper because it isn't from a legit peer reviewed journal.

But, could you let me know where Kuttler goes wrong.

Why is the conservation of momentum and energy not interpreted in this fashion by Bazant or Greening?

Are Kuttler's estimations flawed? And if so, in layman terms, how?

again thanks guys for helping me out.

 

[Calcas]

Interesting thread.

But, don't any of you guys

 

[Thabiguy]

As long as the initial drop of 2 feet is enough to break the board, and all other boards are 2 feet a part, shouldn't they all continue to break even if the ball slows down when breaking through each board?

I think that is right. Only if the initial drop height is higher than 2 feet (or the ball has greater initial speed for some other reason), it is possible for the first board to break and still slow down the collapse.

If the initial drop height is 2 feet or less, then if the boards are capable of stopping the collapse, i.e. if there is a board that will not break, then it can be shown that the first board will also not break.

At least in this idealized example of bowling ball and identical styrofoam boards.

 

[pomeroo]

Your description helps a lot. Thanks for that.

But, is this ignoring that forces are working in both directions?

I mean, the force on the lower intact floors should also be equally transmitted up into into the falling section.

Wouldn't this significantly decrease the kinetic energy of the falling block? And wouldn't this also crush the upper section too?

Also, can we consider the strength of just one floor at a time, or should be consider the strength of the whole lower intact section together? Isn't this important considering the vertical core?

Forgive me, Sizzler, but I can't escape the feeling that you're a twoofer who's trying out the Socratic manner with us. I know I'm cynical, and I'd dearly love to be mistaken, but...

 

[rwguinn]

Your description helps a lot. Thanks for that.

But, is this ignoring that forces are working in both directions?

I mean, the force on the lower intact floors should also be equally transmitted up into into the falling section.

Wouldn't this significantly decrease the kinetic energy of the falling block? And wouldn't this also crush the upper section too?

Also, can we consider the strength of just one floor at a time, or should be consider the strength of the whole lower intact section together? Isn't this important considering the vertical core?

I'm going to take a stab at this, fully ready to munch down on crow if my earlier comment is unfounded:

Sizzler, time to fall is related directly to forces. in a gravity-driven scenario, Force=Mass * acceleration, or F=MA. For the purposes here, we will use an instantaneous mass, M, for any time during the collapse.
for free-fall, A=9.8 meters per second. When there is resistance, say, because the is stuff like 80-odd stories of building below the falling part, we end up with F=9.8M-resistance.
resistance can also be treated as R=Ma, where a is the resultant acceleration. M is still the same M
so, F=M(9.8-a), and we can determine effective acceleration as 9.8-a.
Time for fall is an integral. IF you go throught the math, you get
X=.5(A)t^2, or t=square root(X/(.5A)). Note that function. It is a square root--it is not linear.
Example: an object dropped from the top of a 1300 foot high structure will free-fall to the ground in just under 9 seconds (8.992 seconds)
If it encounters resistance of 50% of gravity, it takes it a whole 12.717 seconds--3.7 seconds longer.

 

[Thabiguy]

Forgive me, Sizzler, but I can't escape the feeling that you're a twoofer who's trying out the Socratic manner with us. I know I'm cynical, and I'd dearly love to be mistaken, but...

pomeroo,
how would you like it if you came to a WWII forum, asked a few perfectly reasonable questions about the holocaust that everybody needs to ask at some point in their life (presumably knowledge of the holocaust is not inherited) and someone told you, "I can't escape the feeling that you're a racist"?

Let's be nice to our new members, and save judgement for when it is due.

These questions are worth answering regardless of who asks them. Openly speculating whether a person is dishonest, just because he's doing what we've been asking strangers to do all along, i.e. ask questions, is not cool.

 

[Sizzler]

Forgive me, Sizzler, but I can't escape the feeling that you're a twoofer who's trying out the Socratic manner with us. I know I'm cynical, and I'd dearly love to be mistaken, but...

I don't exactly know what would make me a twoofer or not.

With that said;

I am still unable to wrap my mind around the fall times of the progressive collapse.

I can't ignore conservation of momentum and energy; especially when the "piledriver" consists of the exact same material that it is crushing.

Help me out guys.

 

[BenBurch]

Interesting thread.

But, don't any of you guys

Caffeine; The new sleep.

 

[BenBurch]

And a Happy Natal Anniversary to rwguinn!!!!

 

[slyjoe]

Happy Birthday rwguinn!

I will make sure to raise a cold one in your honor

 

[Thabiguy]

I am still unable to wrap my mind around the fall times of the progressive collapse.

I can't ignore conservation of momentum and energy; especially when the "piledriver" consists of the exact same material that it is crushing.

Help me out guys.

Well, tell us specifically what you have trouble understanding, and we'll try to explain.

Example: "I can't understand why something would happen; intuitively, it seems more likely that something else should happen, because of reasons. What am I missing?"

 

[rwguinn]

Happy Birthday rwguinn!

I will make sure to raise a cold one in your honor

Thank y'all.
I shall raise a frosty Hatchtoberfest in salute to all those fighting for truth, justice and critical thinking as soon as the sun gets over the yardarm.

and to forestall the curious:
"I'm old enough th want to, and fool enough to try."*
whaterver it is, mostly

*Tom T. Hall

 

[pomeroo]

pomeroo,
how would you like it if you came to a WWII forum, asked a few perfectly reasonable questions about the holocaust that everybody needs to ask at some point in their life (presumably knowledge of the holocaust is not inherited) and someone told you, "I can't escape the feeling that you're a racist"?

Let's be nice to our new members, and save judgement for when it is due.

These questions are worth answering regardless of who asks them. Openly speculating whether a person is dishonest, just because he's doing what we've been asking strangers to do all along, i.e. ask questions, is not cool.

Your point is well-taken, and I'm probably wrong. I'm just saying that I really, really hope I'm wrong.

 

[pomeroo]

I don't exactly know what would make me a twoofer or not.

With that said;

I am still unable to wrap my mind around the fall times of the progressive collapse.

I can't ignore conservation of momentum and energy; especially when the "piledriver" consists of the exact same material that it is crushing.

Help me out guys.

Well, it would make you a twoofer if you believed that a conspiracy originating within the U.S. government orchestrated the attacks of 9/11/01 in order to... let's skip that part. No fantasist has the slightest idea of what the Impossibly Vast Conspiracy's motives were, but they were very bad.

So, you can lay my concerns to rest by simply stating that you acknowledge that America was attacked by well-trained jihadists who hijacked four planes and flew three of them into buildings. Having done so, you can ask your questions about the collapse mechanism free of interruptions.

Incidentally, twoofers routinely prattle nonsense about "conservation of momentum and energy." Your use of the phrase is undoubtedly a coinky-dink.

 

[pomeroo]

Thank y'all.
I shall raise a frosty Hatchtoberfest in salute to all those fighting for truth, justice and critical thinking as soon as the sun gets over the yardarm.

and to forestall the curious:
"I'm old enough th want to, and fool enough to try."*
whaterver it is, mostly

*Tom T. Hall

Happy Birthday, enlightened one!

 

[Sizzler]

Well, tell us specifically what you have trouble understanding, and we'll try to explain.

Example: "I can't understand why something would happen; intuitively, it seems more likely that something else should happen, because of reasons. What am I missing?"

In the above paper I sourced;

When you go through the calculation, which Ken Kuttler did, it takes a lot longer just because of conservation of momentum and energy. Ken’s calculations show numbers over 25 seconds for the complete collapse of Tower 1.26 That is a lot longer than free fall, and longer than the observed destruction of either Tower

When one object hits another, it slows down, even when gravity is the moving force.

It is my gut feeling that the lower 80 or so floors should have resisted the falling upper section enough to atleast slow the collapse well above free fall speed or near free fall speed.

 

[DGM]

I don't exactly know what would make me a twoofer or not.

With that said;

I am still unable to wrap my mind around the fall times of the progressive collapse.

I can't ignore conservation of momentum and energy; especially when the "piledriver" consists of the exact same material that it is crushing.

Help me out guys.

The "pile driver" that you speak of is a lot denser. Although it is made out of the same materials the bottom has lots of air space. The top at the collapse front is a compact mass of concrete, steel and everything else that was on those floors.