David Chandler jumps the shark

[beachnut]

...) see them as only representing floors (portions of mass) which might be freed into instantaneous PE.

I don't see the floors as being able to be liberated into PE, because I see all of the work that must be exerted on the entirety of the structure below it to do so, and consequently all of the work that must be used (subtracted) from the initial KE.

You failed to realize what he meant...

And the second sentence, BS, total nonsense. seek help...

https://www.ic.sunysb.edu/Class/phy122ps/labs/dokuwiki/doku.php?id=phy123summer:lab_5

There are reality based physics resources online, you have failed to find them.

Lost me on the 14/15 BS; a complete lack of education in math/physics/and more...

I have seen this kind of superior knowledge before... a long time ago

https://www.youtube.com/watch?v=MxtN0xxzfsw

 

[GlennB]

No

1/2 ((14/15)m₁(14/15)v₁))²=KE

Really??

Yes, really, like he said. They're related concepts but different.

To illustrate: what's 1 cubic foot minus 6 inches?

 

[ozeco41]

Yes, really, like he said. They're related concepts but different.

To illustrate: what's 1 cubic foot minus 6 inches?

Green??

 

[GlennB]

Green??

9 volts

 

[Notconvinced]

Yes, really, like he said. They're related concepts but different.



To illustrate: what's 1 cubic foot minus 6 inches?

The "really" was sarcasm.....

If you treat the upper and lower sections as blocks then use the mass of the lower section and it's upward vector against gravity. So use m as mass of tower and m2 as (95/110)m

If you treat the collision as only affecting a floor, then you have to deplete the initial momentum by what was used in impact so that's where the 14/15m comes from (with m being weight of upper section in that instance). The next iteration of impact would be 13/15m.


Sent from our shared looking glass platform

 

[jaydeehess]

The "really" was sarcasm.....

If you treat the upper and lower sections as blocks then use the mass of the lower section and it's upward vector against gravity. So use m as mass of tower and m2 as (95/110)m

If you treat the collision as only affecting a floor, then you have to deplete the initial momentum by what was used in impact so that's where the 14/15m comes from (with m being weight of upper section in that instance). The next iteration of impact would be 13/15m.

No, just no. You cannot do that.
What is an "upward vector" of mass?

You are digging a deeper hole wrt your demonstrating a misunderstanding and misapplication of physics.

 

[Dave Rogers]

If you treat the collision as only affecting a floor, then you have to deplete the initial momentum by what was used in impact so that's where the 14/15m comes from (with m being weight of upper section in that instance). The next iteration of impact would be 13/15m.

Only in zero gravity. I think we all agree that, had the Twin Towers been in zero G, they wouldn't have fallen down*.

Dave

*Not least because "down" wouldn't have meant anything.

 

[jaydeehess]

Originally Posted by jaydeehess View Post
So
1/2 m1v12 - m2v2=KE?

No

1/2 ((14/15)m1(14/15)v1))2=KE

WTF, no, just no. That's so bad that calling it wrong does an injustice to the term "wrong".

Originally Posted by jaydeehess View Post
You can no more subtract momentum from energy than you can subtract time from length.

Really??

KE units are_____Kg.meters²/seconds²Momentum units _Kg.meters/seconds

See the difference?

Show me subtraction of momentum from energy and I'll show you subtraction of length from velocity.

 

[Grizzly Bear]

All, the 14 / 15 value that he was posting probably references the floor levels that I was referencing in my calculations for Trade Center 1. I haven't looked at his equation models thoroughly so I can't offer a comment on whether that in part is correct or not, but the two numbers that people seem to have gotten confused about correspond with the floor Heights that I've made reference to

 

[Dave Rogers]

If I took Notconvinced seriously, I'd probably make something of the fact that his nonsense KE equation assumes that both the velocity and the mass of the falling section decrease at every impact. He's not only basing his model on zero gravity, but it seems the lower floors are made of antimatter.

Dave

ETA: Light bulb moment! That's why the mass of the lower floors has an "upward vector against gravity"; he thinks they have negative mass! That would certainly have some implications for collapse modelling.

For some even better comedy moments, should we introduce him to Judy Wood?

 

[pgimeno]

I don't see the floors as being able to be liberated into PE, because I see all of the work that must be exerted on the entirety of the structure below it to do so, and consequently all of the work that must be used (subtracted) from the initial KE.

Then you're not considering the reality of the structure of the towers (or of most buildings). The connections between columns and floors are much, much weaker than the columns themselves. They are designed to support the static weight of one single floor, not that of all floors above it.

One single floor. And statically, not dynamically.

If one floor falls on another, the most likely outcome is that the connections that join it to the columns break. The energy required to break these connections and free the floor is probably several orders of magnitude smaller than the energy required to crush the columns.

Here's how WTC1 and WTC2's connections looked like:

http://911research.wtc7.net/mirrors/guardian2/wtc/fig-2-6.jpg

Here are some actual truss seats marked in a perimeter column panel:

http://www.tms.org/pubs/journals/JOM/0711/figAb.jpg

Here's one already in place, holding the truss that supports the floor:

http://i995.photobucket.com/albums/af74/waypastvne/cap_111463copy.jpg

Here's what happened to them (red arrows):

http://i995.photobucket.com/albums/af74/waypastvne/Screenshot2011-04-21at65211PM.jpg

Or this:

http://911research.com/mirrors/guardian/WTC/fig-D-5.jpg

Now tell me again that the energy required to break these connections and make the floor detach, is comparable to the energy required to hold the whole structure.

 

[Dave Rogers]

I am not a physicist.... but isn't isn't he gravity PE of a mass related to the height it can drop? Mass isn't increasing but as it drops V does. F=ma

I don't think anyone answered this. I am a physicist, and the answer is yes. Potential energy is mgh, mass times acceleration due to gravity times height. As an object falls, its PE is converted to KE, and this was the energy source driving the collapses of the WTC towers. Notconvinced has chosen, insofar as he's able to construct a line of coherent reasoning at all, to pretend this source of energy didn't exist, and concluded that the towers couldn't have fallen. Hence my comments about zero gravity.

Dave

 

[jaydeehess]

I don't think anyone answered this. I am a physicist, and the answer is yes. Potential energy is mgh, mass times acceleration due to gravity times height. As an object falls, its PE is converted to KE, and this was the energy source driving the collapses of the WTC towers. Notconvinced has chosen, insofar as he's able to construct a line of coherent reasoning at all, to pretend this source of energy didn't exist, and concluded that the towers couldn't have fallen. Hence my comments about zero gravity.

Dave

Yes, and if NT would look at it he will see that the units derived by mgh are the same as derived by 1/2mv², and thus the two can be added/subtracted (ie. as PE converts to KE, subtract some PE by converting to KE) ) mathematically. OTOH the units derived for energy are different than those for momentum and thus the two cannot be added and subtracted

 

[GlennB]

If you treat the upper and lower sections as blocks then use the mass of the lower section and it's upward vector against gravity. So use m as mass of tower and m2 as (95/110)m

What's a "mass vector" when it's at home? Mass is a scalar quantity.

If you treat the collision as only affecting a floor, then you have to deplete the initial momentum by what was used in impact so that's where the 14/15m comes from (with m being weight of upper section in that instance). The next iteration of impact would be 13/15m.

Yet again you've ignored the fact that material from the impacted floor also starts to fall.

 

[Dave Rogers]

Yet again you've ignored the fact that material from the impacted floor also starts to fall.

No, he hasn't. He's just subtracted it from the amount falling rather than adding it, for reasons that the rest of us can only guess at.

Dave

 

[Oystein]

I said you lose KE. The lower KE then has to drive it's way through additional resistance while at the same time depleting itself of the equivalent KE. If one story below is crushed, then one story above is crushed, and in that crushing, their net KE is zero. This means your next impact has the KE of the initial falling mass, minus the momentum of one floor. The natural collapse loses KE with each iteration.

Should Tony Szamboti ever see this:

Tony, does that post above make any sense at all to you?

 

[GlennB]

No, he hasn't. He's just subtracted it from the amount falling rather than adding it, for reasons that the rest of us can only guess at.

Dave

Ah. I thought he was deducting one floor's worth of KE of the original falling section for each floor impacted below, until it ran out of KE. Or something. At random.

 

[Oystein]

Thank you. Our differences in understanding this problem is because I see the horizontal lines as representing entire sections of tower (including inner and outer columns) and many of you (I'm fairly sure) see them as only representing floors (portions of mass) which might be freed into instantaneous PE.

I don't see the floors as being able to be liberated into PE, because I see all of the work that must be exerted on the entirety of the structure below it to do so, and consequently all of the work that must be used (subtracted) from the initial KE.

Should Tony Szamboti ever see this:

Tony, does that post above make any sense at all to you?

 

[Oystein]

No

1/2 ((14/15)m₁(14/15)v₁))²=KE
...

Should Tony Szamboti ever see this:

Tony, can you detect anything in this equation that makes sense?

 

[Oystein]

The "really" was sarcasm.....

If you treat the upper and lower sections as blocks then use the mass of the lower section and it's upward vector against gravity. So use m as mass of tower and m2 as (95/110)m

If you treat the collision as only affecting a floor, then you have to deplete the initial momentum by what was used in impact so that's where the 14/15m comes from (with m being weight of upper section in that instance). The next iteration of impact would be 13/15m.

Should Tony Szamboti ever see this:

Tony, does that post above make any sense at all to you?