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Arkan_Wolfshade · 30th August 2006, 12:07 PM

From a CTist

Quote:

A car weighing 18,000 Newtons going 40 Km/h hits a stopped car weighing 14,000 Newtons. The two cars travel off together. In the absence of friction how fast would they move off?

who knows physics?? More specifically who knows conservation of momentum??

Prove it by answering the above question. After that I will get the exact numbers I need and will prove that 9/11 had to involve an alternate energy source/no pancake theory. If someone else can get me exact numbers like weight of building and distribution of weight. number of floors the plane crashed through. height of building and height of each floor including the ceilings. Things like that and the exact time it took the building to fall. I have done this loosely before with semi real numbers and the buildings should have fallen about 10 seconds longer based off theose estimates.

The physics that took place on 9/11 make no sence. Unless the floors below the crash offered about 0 resistence.

conservation of momentum was violated on 9/11 based off physics and the official report.
One conclusion can come out of that, and it is not that physics all the sudden changed. It is that the official story is a fairytale.

I will post the answer below.

Hazzard failed
DEBUNKER failed

Yet they Knew I was not right about my physics. KNEW.

************************************************** **************

initial mass = 18,000/9.81 (F=ma) = 1835 Kg
initial velocity = 40/3600 X 1000 (1000m/km and 3600s/h) = 11m/s
11 X 1835 = 20185 Kgm/s
mass2 = (14,000 + 18,000)/9.81 (F=ma) = 3262 Kg

so using conservation of momentum: m1 X v1 = m2 x v2
you would see that since there was more mass after the crash the speed would be less.

3262 X v2 = 20185

OR

v2 = 20185/3262

so resulting velocity of the two cars traveling off together would be around 6.2 m/s or 22.32 Km/h in the direction the first car was moving.

Want to try again hazzard?
I can add friction of the road to the tires and they could crash on an incline. I could say the cars were in contact for a certain amount of time and how would that matter?

This post has been edited by muddyfrog: Today, 02:00 PM

The thing that jumps out at me is the first sentence; Newtons are a measurement of force, not weight, correct?

Hellbound · 30th August 2006, 12:20 PM

Arkan:

Weight is a measure of force, specifically a measure of the force with which gravity is pulling you.

THe math looks right, actually.

However, what he leaves out is that the material falling from WTC was NOT moving at a constant velocity, it was being CONSTANTLY accelerated. And with each floor hit, it became more massive, meaning the next floor's resistence would slow it down less (using those same momentum laws, as the amount of mass at rest decreases compared to the amoutn of mass in motion, it has less effect on the final velocity).

Arkan_Wolfshade · 30th August 2006, 12:24 PM

Originally Posted by Huntsman

Arkan:

Weight is a measure of force, specifically a measure of the force with which gravity is pulling you.

THe math looks right, actually.

However, what he leaves out is that the material falling from WTC was NOT moving at a constant velocity, it was being CONSTANTLY accelerated. And with each floor hit, it became more massive, meaning the next floor's resistence would slow it down less (using those same momentum laws, as the amount of mass at rest decreases compared to the amoutn of mass in motion, it has less effect on the final velocity).

So, he was using Newtons just to be a smart@$$? For clarification, below the ****** was Hazzard's post, which muddytoad claims is wrong.

Hellbound · 30th August 2006, 12:29 PM

YEah, he used Newtons to be a smart@$$, or (more likely, since he called the math up there wrong) he doesn't understand the difference between weight and mass.

The math up there looks right, though. IF that's HAzzard's, he knows what he's saying.

Arkan_Wolfshade · 30th August 2006, 12:35 PM

Thanks much!

TK0001 · 30th August 2006, 12:37 PM

Originally Posted by Arkan_Wolfshade

Thanks much!

I had a feeling you'd pick that one up.

Hellbound · 30th August 2006, 12:37 PM

Just to add:

Se this high school physics site.

Momentum = mass * velocity. Fairly simple.

What Hazzard did was take the weight in Newtons (which is a force) and apply Newton's llaws to it: Force = mass * acceleration. Since, in a weight, the acceleration is gravity, this means the weight in Newtons divided by 9.81 gives the mass in kilograms.

Now, momentum pre-crash should equal momentum post-crash, so mass * velocity of the single car travelling shoudl equal the mass * velocity of both travelling, which is what Hazzard proceeeded to do.

Muddytoad doesn't know his physics from his anus (which seems to be where he gets his physics from).

RenaissanceBiker · 30th August 2006, 12:38 PM

Well, all those constants like g and the velocity conversions cancel out. You could just say:

V = 18 kN * 40 km/h / (18 kN +14 kN) = 22.5 km/h

/professional engineer

Hellbound · 30th August 2006, 12:38 PM

Originally Posted by RenaissanceBiker

Well, all those constants like g and the velocity conversions cancel out. You could just say:

V = 18 kN * 40 km/h / (18 kN +14 kN) = 22.5 km/h

/professional engineer

Yeah, if you wanna do it the EASY way!

Arkan_Wolfshade · 30th August 2006, 12:40 PM

Originally Posted by RenaissanceBiker

Well, all those constants like g and the velocity conversions cancel out. You could just say:

V = 18 kN * 40 km/h / (18 kN +14 kN) = 22.5 km/h

/professional engineer

Seeing as how I haven't done physics in 15+ yrs, mind if I snag that verbatim? (I have asked muddytoad for clarification on whose text is below the asterisks)

RenaissanceBiker · 30th August 2006, 12:58 PM

Originally Posted by Arkan_Wolfshade

Seeing as how I haven't done physics in 15+ yrs, mind if I snag that verbatim? (I have asked muddytoad for clarification on whose text is below the asterisks)

Just give me credit and buy me a beer if you ever get a chance.

Darth Rotor · 30th August 2006, 01:15 PM

Originally Posted by RenaissanceBiker

Just give me credit and buy me a beer if you ever get a chance.

Isn't conservation of momentum less than 100% efficient for non-rigid bodies, making
M(2)V(2) < M(1)V(1)
for most collisions?

For example, cars' bodies absord "x" amount of energy into their frame, deforming the metal, so that energy used for deformation is not transfered into momentum a la M*V.

Right?

See also golf balls and wooden, forged, or cast clubs, versus the harder (titanium) club faces of the current driver genre.

Entropy can wait for another time.

DR

defaultdotxbe · 30th August 2006, 01:19 PM

Originally Posted by Darth Rotor

Isn't conservation of momentum less than 100% efficient for non-rigid bodies, making
M(2)V(2) < M(1)V(1)
for most collisions?

For example, cars' bodies absord "x" amount of energy into their frame, deforming the metal, so that energy used for deformation is not transfered into momentum a la M*V.

Right?

See also golf balls and wooden, forged, or cast clubs, versus the harder (titanium) club faces of the current driver genre.

Entropy can wait for another time.

DR

yes, the real world is indeed much more complex than HS physics

see also "crumple zones" designed into cars

Arkan_Wolfshade · 30th August 2006, 01:20 PM

Originally Posted by Darth Rotor

Isn't conservation of momentum less than 100% efficient for non-rigid bodies, making
M(2)V(2) < M(1)V(1)
for most collisions?

For example, cars' bodies absord "x" amount of energy into their frame, deforming the metal, so that energy used for deformation is not transfered into momentum a la M*V.

Right?

See also golf balls and wooden, forged, or cast clubs, versus the harder (titanium) club faces of the current driver genre.

Entropy can wait for another time.

DR

Considering muddytoad has already come up with the gem of "I have done this loosely before with semi real numbers and the buildings should have fallen about 10 seconds longer based off theose estimates.

The physics that took place on 9/11 make no sence. Unless the floors below the crash offered about 0 resistence." I don't know that we need too much detail.

deja vu by the way

RenaissanceBiker · 30th August 2006, 01:26 PM

Yes, Darth Rotor, but the problem was stated in the simplest terms. If you are going to ignore friction you are probably ignoring those other pesky little details as well. This is the high school physics solution, not the PE exam solution. That one would require more information.

I'm not sure how muddytoad plans to apply this to his CT of the WTC collapse. I'm almost positive it will be incorrect.

rwguinn · 30th August 2006, 02:20 PM

Originally Posted by Huntsman

Arkan:

Weight is a measure of force, specifically a measure of the force with which gravity is pulling you.

THe math looks right, actually.

However, what he leaves out is that the material falling from WTC was NOT moving at a constant velocity, it was being CONSTANTLY accelerated. And with each floor hit, it became more massive, meaning the next floor's resistence would slow it down less (using those same momentum laws, as the amount of mass at rest decreases compared to the amoutn of mass in motion, it has less effect on the final velocity).

er--nevermind.. I just saw the "compared to the amoutn of mass in motion" part.
you are correct--you only have to deal with the mass of one floor at a time doing the resisting, while the to-be-resisted grows with the addition of each floor...

boooeee · 30th August 2006, 02:41 PM

Originally Posted by Darth Rotor

Isn't conservation of momentum less than 100% efficient for non-rigid bodies, making
M(2)V(2) < M(1)V(1)
for most collisions?

For example, cars' bodies absord "x" amount of energy into their frame, deforming the metal, so that energy used for deformation is not transfered into momentum a la M*V.

Right?

See also golf balls and wooden, forged, or cast clubs, versus the harder (titanium) club faces of the current driver genre.

Entropy can wait for another time.

DR

Not exactly. Conservation of kinetic energy is not 100% effecient for non-rigid bodies. When two non-rigid bodies collide, some of their energy is dissipated through heat. However, the total momentum is 100% conserved, assuming they're on a frictionless surface.

I'm being nitpicky, but your post above seemed to indicate that momentum could be lost due to the two cars interaction with eachother. Momentum is only lost if the two cars interact with an outside body (e.g. the ground).

CurtC · 30th August 2006, 03:26 PM

Originally Posted by boooeee

Not exactly. Conservation of kinetic energy is not 100% effecient for non-rigid bodies. When two non-rigid bodies collide, some of their energy is dissipated through heat. However, the total momentum is 100% conserved, assuming they're on a frictionless surface.

And those of us who are really picky point out that momentum is 100% conserved, even counting friction; you just have to include the Earth in the calculations.

boooeee · 30th August 2006, 03:36 PM

Originally Posted by CurtC

And those of us who are really picky point out that momentum is 100% conserved, even counting friction; you just have to include the Earth in the calculations.

True, true. I meant the momentum of the two bodies only. But I can hardly complain about nitpicks at this point.

Reminds me of one of my favorite physics brain teasers: If England changed it's driving laws such that everybody had to drive on the right side of the road, would the day get shorter, longer, or stay the same?

tracer · 30th August 2006, 03:58 PM

Originally Posted by boooeee

Reminds me of one of my favorite physics brain teasers: If England changed it's driving laws such that everybody had to drive on the right side of the road, would the day get shorter, longer, or stay the same?

The day would get longer, for a while, because all the road workers would have to put in a huge amount of Overtime changing the signs around.

R.Mackey · 30th August 2006, 04:43 PM

Originally Posted by Arkan_Wolfshade

So, he was using Newtons just to be a smart@$$? For clarification, below the ****** was Hazzard's post, which muddytoad claims is wrong.

Looks like you've already got your answer. Conservation of Momentum is correct, m_both v_both = m₁v₁ + m₂v₂, the rest of the kinetic energy is dissipated by smashing up the cars.

Newtons is correct. In metric, you measure weight in Newtons. However, what you really want in the Conservation of Momentum equation is mass, so you need to divide by 10 kg / N -- Ok, it's 9.8 m/s², but 10 is close enough -- to get the mass. His answer wasn't a smartazz answer, just not elegant.

The whole "Conservation of Momentum" argument denying the pancake theory is precisely the drivel that Gordon Ross has put forth, as seen in the June issue of the "Journal for 9/11 Studies" linked through "Scholars for 9/11 Truth." I note some blatant hypocrisy in that the "Journal" is not peer-reviewed, contrary to the claim in their portal... truth indeed... Anyway, Dr. Greening does a good job taking Ross to task, and Ross is still trying to get the last word.

I've critiqued Ross's paper myself, first in this post and then addressing the follow-ups, as Greening rebuts and Ross still gets it wrong, here. The problem with arguing against pancake collapse via a momentum and energy conservation argument is that the problem is difficult to set up completely -- this is Gordon Ross's mistake. His argument is that the lower part of the WTC tower would rebound elastically when hit to match the speed dictated by conservation of momentum, this rebound sinks a good chunk of the kinetic energy, and the net result is just barely under the failure energy required to destroy another floor. What he leaves out is that the new kinetic energy must then be dissipated as well -- he stops the calculation with several floors still moving downward, no lie -- and that transmitting energy to make floors below the contact floor also rebound induces further strain on the support columns, due to the floors' inertia, that he doesn't account for.

Ross also makes some bad assumptions about how much of the structure will sense the collision and rebound before the top starts to crumble. He further insists on other events that must take place before failure must progress (like crushing both contact floors completely to powder) that are clearly not required. In his zeal to add detail to the situation, he leaves out several important components of the true energy balance. I'll give him the benefit of the doubt and say that it was a series of honest mistakes, the kind that would have been caught were this a true peer-reviewed journal. Or if they sought any criticism at all.

To relate this to your crashing cars example, crashing the two cars on a frictionless surface makes the calculation easy, but it isn't a good model for our system. ("Easy, but wrong.") The WTC towers were fixed on the ground. The various floors are coupled with elastic (and then plastic, after being driven beyond their elastic limits) columns. Think of it instead as crashing one car into another that's held fixed by a stiff spring, a spring that breaks once either its stress or its strain exceeds a certain value.

I don't have much confidence the CTer in question will be able to set this problem up correctly given what you've shown me so far. Big surprise, I know.

fuelair · 30th August 2006, 05:09 PM

Originally Posted by RenaissanceBiker

Yes, Darth Rotor, but the problem was stated in the simplest terms. If you are going to ignore friction you are probably ignoring those other pesky little details as well. This is the high school physics solution, not the PE exam solution. That one would require more information.

I'm not sure how muddytoad plans to apply this to his CT of the WTC collapse. I'm almost positive it will be incorrect.

And without friction or gravity (towers, not cars) how is this related??

gumboot · 30th August 2006, 11:25 PM

Originally Posted by tracer

The day would get longer, for a while, because all the road workers would have to put in a huge amount of Overtime changing the signs around.

Actually one of the Scandanavian countries did it overnight... (was it Sweden???).

-Andrew

RenaissanceBiker · 31st August 2006, 04:50 AM

Look at it this way, if we only look at conservation of momentum and ignore conservation of energy, nothing would ever fall. The upper floors of the WTC had a downard velocity of zero before the supports were taken out. Once the thermite charges built into the structure detonated, the downward momentum would remain zero.

The apple in Newton's tree had an initial downward momentum of zero. There's no way it could have fallen by itself. It had to have been pushed! Now we know the conspiracy goes back over 200 years!

gumboot · 31st August 2006, 05:03 AM

Originally Posted by RenaissanceBiker

The apple in Newton's tree had an initial downward momentum of zero. There's no way it could have fallen by itself. It had to have been pushed! Now we know the conspiracy goes back over 200 years!

The apple fell because the thermite larvae inside it ate its core...

-Andrew

NobbyNobbs · 31st August 2006, 05:12 AM

The fact that he used weight instead of mass doesn't bother me, because *everybody* mixes those two up. In fact, I was surprised he got the units for weight right. Then I got to thinking: why did he use Newtons? Not very many people (in the U.S., at least) have a good idea how much a Newton is. So I did some conversions...

18,000 Newtons=39,600 pounds, or a little under 20 tons.
14,000 Newtons=30,800 pounds, or almost 15.5 tons.

What kind of car is this guy driving???

RenaissanceBiker · 31st August 2006, 05:39 AM

Originally Posted by gumboot

The apple fell because the thermite larvae inside it ate its core...

-Andrew

The larvae was intentionally placed in the apple core as it grew. That's why there was no evidence of a larvae insertion point.

It's true.

jhunter1163 · 31st August 2006, 05:50 AM

A car weighing 18,000 Newtons going 40 Km/h hits a stopped car weighing 14,000 Newtons. The two cars travel off together. In the absence of friction how fast would they move off?

I don't think cars made of Newtons would be very rigid. They would have very large crumple zones too. On the other hand, cleanup after accidents could be accomplished by an elementary school class with a few gallons of milk.

gruk · 31st August 2006, 05:52 AM

Originally Posted by gumboot

Actually one of the Scandanavian countries did it overnight... (was it Sweden???).

-Andrew

Yep, September 1967.

Wikipedia article

NobbyNobbs · 31st August 2006, 07:06 AM

Originally Posted by NobbyNobbs

The fact that he used weight instead of mass doesn't bother me, because *everybody* mixes those two up. In fact, I was surprised he got the units for weight right. Then I got to thinking: why did he use Newtons? Not very many people (in the U.S., at least) have a good idea how much a Newton is. So I did some conversions...

18,000 Newtons=39,600 pounds, or a little under 20 tons.
14,000 Newtons=30,800 pounds, or almost 15.5 tons.

What kind of car is this guy driving???

Oops. I was using the wrong conversion factor. Please ignore the above.

18,000 Newtons is 2 tons. 14,000 Newtons is 1.5 tons. Much more reasonable.

RenaissanceBiker · 31st August 2006, 07:20 AM

Ah, yes. You were using Figanewtons.

Darth Rotor · 31st August 2006, 07:24 AM

Originally Posted by jhunter1163

A car weighing 18,000 Newtons going 40 Km/h hits a stopped car weighing 14,000 Newtons. The two cars travel off together. In the absence of friction how fast would they move off?

I don't think cars made of Newtons would be very rigid. They would have very large crumple zones too. On the other hand, cleanup after accidents could be accomplished by an elementary school class with a few gallons of milk.

That would be "crumble zones" but otherwise I completely concur with your analysis.

Disclaimer from Nabisco: These analyses were performed by professional skeptics. Don't try this in your own home. No Fig Newtons were actually harmed during these analyses, although a few brain cells were killed by colleral beer damage.

DR

Arkan_Wolfshade · 31st August 2006, 11:21 AM

fwiw, from a good friend of mine who is an ME at Bridgestone/Firestone

Quote:

Okay, I think I remember this.

Mo*v = Mo*v
Mo of moving car: 18000 * 40 = 720000
(18000+14000)*v = 720000
V=22.5 kph

So assuming no energy is lost and the all mass is conserved in the
system (i.e. drivers are not ejected from car, etc), the jumbled mess
will move off at a stately 22.5 kph (14mph) across your hypothetical
frictionless surface.

This, of course, makes me curious as to the question of "Exactly how
good are the energy absorbing 'crumple zones' in soaking up the Mo?"
Let alone the energy lost in vehicle/ground friction and whatnot.

Arkan_Wolfshade · 31st August 2006, 11:38 AM

Oh, and muddytoad clarified, the numbers in the bottom of his/her post are his/her calc's, not that of Hazzard.

jskowron · 31st August 2006, 12:04 PM

Even assuming the physics/math were correct, the CT logic would still be along the lines of

"since two outrageously huge automobiles crashing into each other would have this velocity......the government must have blown up the WTC buildings"

They resort to physics/math to appear to be more of an authority than they are, and to introduce a strawman (e.g. "your book physics can't perfectly explain the ultra-complex, real world, probably never before thought of collapse of giant skyscrapers that have been hit by jets, and since it is unlikely that "physics" is wrong, the official explanation of what happened must be.")

Arkan_Wolfshade · 31st August 2006, 02:24 PM

Originally Posted by Arkan_Wolfshade

fwiw, from a good friend of mine who is an ME at Bridgestone/Firestone

Minor correction has been passed along to me:

Quote:

Well, if you use this in a post, I made a typo. Momentum = Mass *
Velocity. So its M*V = M*V, not Mo*V = M0*V. I was overzealous typing
out my Mo's.

As always, transparency is the best policy.

Verde · 31st August 2006, 03:14 PM

Originally Posted by boooeee

If England changed it's driving laws such that everybody had to drive on the right side of the road, would the day get shorter, longer, or stay the same?

As I recall, the actual discussion about this had the buses and lorries moving over first as a test period, and if successful the cars would change over the following month.

30th August 2006, 12:07 PM	#1
Arkan_Wolfshade Philosopher Join Date: Jan 2006 Location: Making Mytheon come to life Posts: 7,158	Physics assistence por favor From a CTist Quote: A car weighing 18,000 Newtons going 40 Km/h hits a stopped car weighing 14,000 Newtons. The two cars travel off together. In the absence of friction how fast would they move off? who knows physics?? More specifically who knows conservation of momentum?? Prove it by answering the above question. After that I will get the exact numbers I need and will prove that 9/11 had to involve an alternate energy source/no pancake theory. If someone else can get me exact numbers like weight of building and distribution of weight. number of floors the plane crashed through. height of building and height of each floor including the ceilings. Things like that and the exact time it took the building to fall. I have done this loosely before with semi real numbers and the buildings should have fallen about 10 seconds longer based off theose estimates. The physics that took place on 9/11 make no sence. Unless the floors below the crash offered about 0 resistence. conservation of momentum was violated on 9/11 based off physics and the official report. One conclusion can come out of that, and it is not that physics all the sudden changed. It is that the official story is a fairytale. I will post the answer below. Hazzard failed DEBUNKER failed Yet they Knew I was not right about my physics. KNEW. ************************************************ ************ initial mass = 18,000/9.81 (F=ma) = 1835 Kg initial velocity = 40/3600 X 1000 (1000m/km and 3600s/h) = 11m/s 11 X 1835 = 20185 Kgm/s mass2 = (14,000 + 18,000)/9.81 (F=ma) = 3262 Kg so using conservation of momentum: m1 X v1 = m2 x v2 you would see that since there was more mass after the crash the speed would be less. 3262 X v2 = 20185 OR v2 = 20185/3262 so resulting velocity of the two cars traveling off together would be around 6.2 m/s or 22.32 Km/h in the direction the first car was moving. Want to try again hazzard? I can add friction of the road to the tires and they could crash on an incline. I could say the cars were in contact for a certain amount of time and how would that matter? This post has been edited by muddyfrog: Today, 02:00 PM The thing that jumps out at me is the first sentence; Newtons are a measurement of force, not weight, correct?
	__________________ Amy: You should try homeopathic medicine, Bender. Try some zinc. Bender: I am forty percent zinc. Amy: Then take some echinacea, or St. John's Wort. Professor: Or a big fat placebo. It's all the same crap.

30th August 2006, 12:24 PM	#3
Arkan_Wolfshade Philosopher Join Date: Jan 2006 Location: Making Mytheon come to life Posts: 7,158	Originally Posted by Huntsman Arkan: Weight is a measure of force, specifically a measure of the force with which gravity is pulling you. THe math looks right, actually. However, what he leaves out is that the material falling from WTC was NOT moving at a constant velocity, it was being CONSTANTLY accelerated. And with each floor hit, it became more massive, meaning the next floor's resistence would slow it down less (using those same momentum laws, as the amount of mass at rest decreases compared to the amoutn of mass in motion, it has less effect on the final velocity). So, he was using Newtons just to be a smart@$$? For clarification, below the ****** was Hazzard's post, which muddytoad claims is wrong.
	__________________ Amy: You should try homeopathic medicine, Bender. Try some zinc. Bender: I am forty percent zinc. Amy: Then take some echinacea, or St. John's Wort. Professor: Or a big fat placebo. It's all the same crap.

30th August 2006, 12:35 PM	#5
Arkan_Wolfshade Philosopher Join Date: Jan 2006 Location: Making Mytheon come to life Posts: 7,158	Thanks much!
	__________________ Amy: You should try homeopathic medicine, Bender. Try some zinc. Bender: I am forty percent zinc. Amy: Then take some echinacea, or St. John's Wort. Professor: Or a big fat placebo. It's all the same crap.

30th August 2006, 12:37 PM	#6
TK0001 Muse Join Date: Aug 2006 Posts: 595	Originally Posted by Arkan_Wolfshade Thanks much! I had a feeling you'd pick that one up.
TK0001 Muse Join Date: Aug 2006 Posts: 595

30th August 2006, 12:38 PM	#8
RenaissanceBiker Eats shoots and leaves. Join Date: Aug 2006 Location: South Carolina Posts: 6,869	Well, all those constants like g and the velocity conversions cancel out. You could just say: V = 18 kN * 40 km/h / (18 kN +14 kN) = 22.5 km/h /professional engineer
	__________________ "Truth does not contradict truth." - St. Augustine "Faith often contradicts faith. Therefore faith is not an indication of truth." - RenaissanceBiker

30th August 2006, 12:20 PM	#2
Hellbound Abiogenic Spongiform Join Date: Sep 2002 Location: In a handbasket Posts: 9,030	Arkan: Weight is a measure of force, specifically a measure of the force with which gravity is pulling you. THe math looks right, actually. However, what he leaves out is that the material falling from WTC was NOT moving at a constant velocity, it was being CONSTANTLY accelerated. And with each floor hit, it became more massive, meaning the next floor's resistence would slow it down less (using those same momentum laws, as the amount of mass at rest decreases compared to the amoutn of mass in motion, it has less effect on the final velocity).

30th August 2006, 12:29 PM	#4
Hellbound Abiogenic Spongiform Join Date: Sep 2002 Location: In a handbasket Posts: 9,030	YEah, he used Newtons to be a smart@$$, or (more likely, since he called the math up there wrong) he doesn't understand the difference between weight and mass. The math up there looks right, though. IF that's HAzzard's, he knows what he's saying.

30th August 2006, 12:40 PM	#10
Arkan_Wolfshade Philosopher Join Date: Jan 2006 Location: Making Mytheon come to life Posts: 7,158	Originally Posted by RenaissanceBiker Well, all those constants like g and the velocity conversions cancel out. You could just say: V = 18 kN * 40 km/h / (18 kN +14 kN) = 22.5 km/h /professional engineer Seeing as how I haven't done physics in 15+ yrs, mind if I snag that verbatim? (I have asked muddytoad for clarification on whose text is below the asterisks)
	__________________ Amy: You should try homeopathic medicine, Bender. Try some zinc. Bender: I am forty percent zinc. Amy: Then take some echinacea, or St. John's Wort. Professor: Or a big fat placebo. It's all the same crap.

30th August 2006, 12:58 PM	#11
RenaissanceBiker Eats shoots and leaves. Join Date: Aug 2006 Location: South Carolina Posts: 6,869	Originally Posted by Arkan_Wolfshade Seeing as how I haven't done physics in 15+ yrs, mind if I snag that verbatim? (I have asked muddytoad for clarification on whose text is below the asterisks) Just give me credit and buy me a beer if you ever get a chance.
	__________________ "Truth does not contradict truth." - St. Augustine "Faith often contradicts faith. Therefore faith is not an indication of truth." - RenaissanceBiker

30th August 2006, 01:15 PM	#12
Darth Rotor Salted Sith Cynic Join Date: Aug 2006 Location: Rat cheer Posts: 34,379	Originally Posted by RenaissanceBiker Just give me credit and buy me a beer if you ever get a chance. Isn't conservation of momentum less than 100% efficient for non-rigid bodies, making M(2)V(2) < M(1)V(1) for most collisions? For example, cars' bodies absord "x" amount of energy into their frame, deforming the metal, so that energy used for deformation is not transfered into momentum a la M*V. Right? See also golf balls and wooden, forged, or cast clubs, versus the harder (titanium) club faces of the current driver genre. Entropy can wait for another time. DR
	__________________ Helicopters don't so much fly as beat the air into submission. "Jesus wept, but did He laugh?"--F.H. Buckley____"There is one thing that was too great for God to show us when He walked upon our earth ... His mirth." --Chesterton__"If the barbarian in us is excised, so is our humanity."--D'rok__ "I only use my gun whenever kindness fails."-- Robert Earl Keen__"Sturgeon spares none.". -- The Marquis Last edited by Darth Rotor; 30th August 2006 at 01:17 PM.

30th August 2006, 01:19 PM	#13
defaultdotxbe Drunken Shikigami Join Date: Jul 2006 Location: The Dark Side of the Sun Posts: 7,482	Originally Posted by Darth Rotor Isn't conservation of momentum less than 100% efficient for non-rigid bodies, making M(2)V(2) < M(1)V(1) for most collisions? For example, cars' bodies absord "x" amount of energy into their frame, deforming the metal, so that energy used for deformation is not transfered into momentum a la M*V. Right? See also golf balls and wooden, forged, or cast clubs, versus the harder (titanium) club faces of the current driver genre. Entropy can wait for another time. DR yes, the real world is indeed much more complex than HS physics see also "crumple zones" designed into cars
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30th August 2006, 01:20 PM	#14
Arkan_Wolfshade Philosopher Join Date: Jan 2006 Location: Making Mytheon come to life Posts: 7,158	Originally Posted by Darth Rotor Isn't conservation of momentum less than 100% efficient for non-rigid bodies, making M(2)V(2) < M(1)V(1) for most collisions? For example, cars' bodies absord "x" amount of energy into their frame, deforming the metal, so that energy used for deformation is not transfered into momentum a la M*V. Right? See also golf balls and wooden, forged, or cast clubs, versus the harder (titanium) club faces of the current driver genre. Entropy can wait for another time. DR Considering muddytoad has already come up with the gem of "I have done this loosely before with semi real numbers and the buildings should have fallen about 10 seconds longer based off theose estimates. The physics that took place on 9/11 make no sence. Unless the floors below the crash offered about 0 resistence." I don't know that we need too much detail. deja vu by the way
	__________________ Amy: You should try homeopathic medicine, Bender. Try some zinc. Bender: I am forty percent zinc. Amy: Then take some echinacea, or St. John's Wort. Professor: Or a big fat placebo. It's all the same crap.

30th August 2006, 01:26 PM	#15
RenaissanceBiker Eats shoots and leaves. Join Date: Aug 2006 Location: South Carolina Posts: 6,869	Yes, Darth Rotor, but the problem was stated in the simplest terms. If you are going to ignore friction you are probably ignoring those other pesky little details as well. This is the high school physics solution, not the PE exam solution. That one would require more information. I'm not sure how muddytoad plans to apply this to his CT of the WTC collapse. I'm almost positive it will be incorrect.
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30th August 2006, 02:20 PM	#16
rwguinn Philosopher Join Date: Apr 2003 Location: 16 miles from 7 lakes Posts: 8,508	Originally Posted by Huntsman Arkan: Weight is a measure of force, specifically a measure of the force with which gravity is pulling you. THe math looks right, actually. However, what he leaves out is that the material falling from WTC was NOT moving at a constant velocity, it was being CONSTANTLY accelerated. And with each floor hit, it became more massive, meaning the next floor's resistence would slow it down less (using those same momentum laws, as the amount of mass at rest decreases compared to the amoutn of mass in motion, it has less effect on the final velocity). er--nevermind.. I just saw the "compared to the amoutn of mass in motion" part. you are correct--you only have to deal with the mass of one floor at a time doing the resisting, while the to-be-resisted grows with the addition of each floor...
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30th August 2006, 02:41 PM	#17
boooeee Dart Fener Join Date: Aug 2002 Location: The Lando System Posts: 2,403	Originally Posted by Darth Rotor Isn't conservation of momentum less than 100% efficient for non-rigid bodies, making M(2)V(2) < M(1)V(1) for most collisions? For example, cars' bodies absord "x" amount of energy into their frame, deforming the metal, so that energy used for deformation is not transfered into momentum a la M*V. Right? See also golf balls and wooden, forged, or cast clubs, versus the harder (titanium) club faces of the current driver genre. Entropy can wait for another time. DR Not exactly. Conservation of kinetic energy is not 100% effecient for non-rigid bodies. When two non-rigid bodies collide, some of their energy is dissipated through heat. However, the total momentum is 100% conserved, assuming they're on a frictionless surface. I'm being nitpicky, but your post above seemed to indicate that momentum could be lost due to the two cars interaction with eachother. Momentum is only lost if the two cars interact with an outside body (e.g. the ground).
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30th August 2006, 03:26 PM	#18
CurtC Illuminator Join Date: Aug 2001 Location: Dallas, TX Posts: 4,761	Originally Posted by boooeee Not exactly. Conservation of kinetic energy is not 100% effecient for non-rigid bodies. When two non-rigid bodies collide, some of their energy is dissipated through heat. However, the total momentum is 100% conserved, assuming they're on a frictionless surface. And those of us who are really picky point out that momentum is 100% conserved, even counting friction; you just have to include the Earth in the calculations.

30th August 2006, 03:36 PM	#19
boooeee Dart Fener Join Date: Aug 2002 Location: The Lando System Posts: 2,403	Originally Posted by CurtC And those of us who are really picky point out that momentum is 100% conserved, even counting friction; you just have to include the Earth in the calculations. True, true. I meant the momentum of the two bodies only. But I can hardly complain about nitpicks at this point. Reminds me of one of my favorite physics brain teasers: If England changed it's driving laws such that everybody had to drive on the right side of the road, would the day get shorter, longer, or stay the same?
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30th August 2006, 03:58 PM	#20
tracer Graduate Poster Join Date: Jul 2003 Location: Silicon Valley, Calif. Posts: 1,356	Originally Posted by boooeee Reminds me of one of my favorite physics brain teasers: If England changed it's driving laws such that everybody had to drive on the right side of the road, would the day get shorter, longer, or stay the same? The day would get longer, for a while, because all the road workers would have to put in a huge amount of Overtime changing the signs around.

30th August 2006, 04:43 PM	#21
R.Mackey Philosopher Join Date: Apr 2006 Location: The armpit of L.A. Posts: 7,857	Originally Posted by Arkan_Wolfshade So, he was using Newtons just to be a smart@$$? For clarification, below the ****** was Hazzard's post, which muddytoad claims is wrong. Looks like you've already got your answer. Conservation of Momentum is correct, m_both v_both = m₁v₁ + m₂v₂, the rest of the kinetic energy is dissipated by smashing up the cars. Newtons is correct. In metric, you measure weight in Newtons. However, what you really want in the Conservation of Momentum equation is mass, so you need to divide by 10 kg / N -- Ok, it's 9.8 m/s², but 10 is close enough -- to get the mass. His answer wasn't a smartazz answer, just not elegant. The whole "Conservation of Momentum" argument denying the pancake theory is precisely the drivel that Gordon Ross has put forth, as seen in the June issue of the "Journal for 9/11 Studies" linked through "Scholars for 9/11 Truth." I note some blatant hypocrisy in that the "Journal" is not peer-reviewed, contrary to the claim in their portal... truth indeed... Anyway, Dr. Greening does a good job taking Ross to task, and Ross is still trying to get the last word. I've critiqued Ross's paper myself, first in this post and then addressing the follow-ups, as Greening rebuts and Ross still gets it wrong, here. The problem with arguing against pancake collapse via a momentum and energy conservation argument is that the problem is difficult to set up completely -- this is Gordon Ross's mistake. His argument is that the lower part of the WTC tower would rebound elastically when hit to match the speed dictated by conservation of momentum, this rebound sinks a good chunk of the kinetic energy, and the net result is just barely under the failure energy required to destroy another floor. What he leaves out is that the new kinetic energy must then be dissipated as well -- he stops the calculation with several floors still moving downward, no lie -- and that transmitting energy to make floors below the contact floor also rebound induces further strain on the support columns, due to the floors' inertia, that he doesn't account for. Ross also makes some bad assumptions about how much of the structure will sense the collision and rebound before the top starts to crumble. He further insists on other events that must take place before failure must progress (like crushing both contact floors completely to powder) that are clearly not required. In his zeal to add detail to the situation, he leaves out several important components of the true energy balance. I'll give him the benefit of the doubt and say that it was a series of honest mistakes, the kind that would have been caught were this a true peer-reviewed journal. Or if they sought any criticism at all. To relate this to your crashing cars example, crashing the two cars on a frictionless surface makes the calculation easy, but it isn't a good model for our system. ("Easy, but wrong.") The WTC towers were fixed on the ground. The various floors are coupled with elastic (and then plastic, after being driven beyond their elastic limits) columns. Think of it instead as crashing one car into another that's held fixed by a stiff spring, a spring that breaks once either its stress or its strain exceeds a certain value. I don't have much confidence the CTer in question will be able to set this problem up correctly given what you've shown me so far. Big surprise, I know.

30th August 2006, 05:09 PM	#22
fuelair Cythraul Enfys Join Date: May 2006 Posts: 29,321	Originally Posted by RenaissanceBiker Yes, Darth Rotor, but the problem was stated in the simplest terms. If you are going to ignore friction you are probably ignoring those other pesky little details as well. This is the high school physics solution, not the PE exam solution. That one would require more information. I'm not sure how muddytoad plans to apply this to his CT of the WTC collapse. I'm almost positive it will be incorrect. And without friction or gravity (towers, not cars) how is this related??
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30th August 2006, 11:25 PM	#23
gumboot lorcutus.tolere Join Date: Jun 2006 Location: New Zealand Posts: 23,196	Originally Posted by tracer The day would get longer, for a while, because all the road workers would have to put in a huge amount of Overtime changing the signs around. Actually one of the Scandanavian countries did it overnight... (was it Sweden???). -Andrew
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31st August 2006, 04:50 AM	#24
RenaissanceBiker Eats shoots and leaves. Join Date: Aug 2006 Location: South Carolina Posts: 6,869	Look at it this way, if we only look at conservation of momentum and ignore conservation of energy, nothing would ever fall. The upper floors of the WTC had a downard velocity of zero before the supports were taken out. Once the thermite charges built into the structure detonated, the downward momentum would remain zero. The apple in Newton's tree had an initial downward momentum of zero. There's no way it could have fallen by itself. It had to have been pushed! Now we know the conspiracy goes back over 200 years!
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31st August 2006, 05:03 AM	#25
gumboot lorcutus.tolere Join Date: Jun 2006 Location: New Zealand Posts: 23,196	Originally Posted by RenaissanceBiker The apple in Newton's tree had an initial downward momentum of zero. There's no way it could have fallen by itself. It had to have been pushed! Now we know the conspiracy goes back over 200 years! The apple fell because the thermite larvae inside it ate its core... -Andrew
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31st August 2006, 05:12 AM	#26
NobbyNobbs Gazerbeam's Protege Join Date: Apr 2006 Location: The Mended Drum Posts: 5,631	The fact that he used weight instead of mass doesn't bother me, because everybody mixes those two up. In fact, I was surprised he got the units for weight right. Then I got to thinking: why did he use Newtons? Not very many people (in the U.S., at least) have a good idea how much a Newton is. So I did some conversions... 18,000 Newtons=39,600 pounds, or a little under 20 tons. 14,000 Newtons=30,800 pounds, or almost 15.5 tons. What kind of car is this guy driving???
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31st August 2006, 05:39 AM	#27
RenaissanceBiker Eats shoots and leaves. Join Date: Aug 2006 Location: South Carolina Posts: 6,869	Originally Posted by gumboot The apple fell because the thermite larvae inside it ate its core... -Andrew The larvae was intentionally placed in the apple core as it grew. That's why there was no evidence of a larvae insertion point. It's true.
	__________________ "Truth does not contradict truth." - St. Augustine "Faith often contradicts faith. Therefore faith is not an indication of truth." - RenaissanceBiker

31st August 2006, 05:50 AM	#28
jhunter1163 Beer-Swilling Semiliterate Moderator Join Date: Jul 2006 Location: Room 118, Bohemian Grove Marriott Posts: 15,900	A car weighing 18,000 Newtons going 40 Km/h hits a stopped car weighing 14,000 Newtons. The two cars travel off together. In the absence of friction how fast would they move off? I don't think cars made of Newtons would be very rigid. They would have very large crumple zones too. On the other hand, cleanup after accidents could be accomplished by an elementary school class with a few gallons of milk.

31st August 2006, 05:52 AM	#29
gruk Thinker Join Date: Sep 2005 Location: Greater London Area, UK Posts: 159	Originally Posted by gumboot Actually one of the Scandanavian countries did it overnight... (was it Sweden???). -Andrew Yep, September 1967. Wikipedia article

31st August 2006, 07:06 AM	#30
NobbyNobbs Gazerbeam's Protege Join Date: Apr 2006 Location: The Mended Drum Posts: 5,631	Originally Posted by NobbyNobbs The fact that he used weight instead of mass doesn't bother me, because everybody mixes those two up. In fact, I was surprised he got the units for weight right. Then I got to thinking: why did he use Newtons? Not very many people (in the U.S., at least) have a good idea how much a Newton is. So I did some conversions... 18,000 Newtons=39,600 pounds, or a little under 20 tons. 14,000 Newtons=30,800 pounds, or almost 15.5 tons. What kind of car is this guy driving??? Oops. I was using the wrong conversion factor. Please ignore the above. 18,000 Newtons is 2 tons. 14,000 Newtons is 1.5 tons. Much more reasonable.
	__________________ I wish someone would find something I wrote on this board to be sig-worthy, thereby effectively granting me immortality.--Antiquehunter The gods do not deduct from a man's allotted years on earth the time spent eating butterscotch pudding. AMERICA! NUMBER 1 IN PARTICLE PHYSICS SINCE JULY 4TH, 1776!!! --SusanConstant

31st August 2006, 07:20 AM	#31
RenaissanceBiker Eats shoots and leaves. Join Date: Aug 2006 Location: South Carolina Posts: 6,869	Ah, yes. You were using Figanewtons.
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31st August 2006, 07:24 AM	#32
Darth Rotor Salted Sith Cynic Join Date: Aug 2006 Location: Rat cheer Posts: 34,379	Originally Posted by jhunter1163 A car weighing 18,000 Newtons going 40 Km/h hits a stopped car weighing 14,000 Newtons. The two cars travel off together. In the absence of friction how fast would they move off? I don't think cars made of Newtons would be very rigid. They would have very large crumple zones too. On the other hand, cleanup after accidents could be accomplished by an elementary school class with a few gallons of milk. That would be "crumble zones" but otherwise I completely concur with your analysis. Disclaimer from Nabisco: These analyses were performed by professional skeptics. Don't try this in your own home. No Fig Newtons were actually harmed during these analyses, although a few brain cells were killed by colleral beer damage. DR
	__________________ Helicopters don't so much fly as beat the air into submission. "Jesus wept, but did He laugh?"--F.H. Buckley____"There is one thing that was too great for God to show us when He walked upon our earth ... His mirth." --Chesterton__"If the barbarian in us is excised, so is our humanity."--D'rok__ "I only use my gun whenever kindness fails."-- Robert Earl Keen__"Sturgeon spares none.". -- The Marquis

31st August 2006, 11:21 AM	#33
Arkan_Wolfshade Philosopher Join Date: Jan 2006 Location: Making Mytheon come to life Posts: 7,158	fwiw, from a good friend of mine who is an ME at Bridgestone/Firestone Quote: Okay, I think I remember this. Mov = Mov Mo of moving car: 18000 * 40 = 720000 (18000+14000)*v = 720000 V=22.5 kph So assuming no energy is lost and the all mass is conserved in the system (i.e. drivers are not ejected from car, etc), the jumbled mess will move off at a stately 22.5 kph (14mph) across your hypothetical frictionless surface. This, of course, makes me curious as to the question of "Exactly how good are the energy absorbing 'crumple zones' in soaking up the Mo?" Let alone the energy lost in vehicle/ground friction and whatnot.
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31st August 2006, 11:38 AM	#34
Arkan_Wolfshade Philosopher Join Date: Jan 2006 Location: Making Mytheon come to life Posts: 7,158	Oh, and muddytoad clarified, the numbers in the bottom of his/her post are his/her calc's, not that of Hazzard.
	__________________ Amy: You should try homeopathic medicine, Bender. Try some zinc. Bender: I am forty percent zinc. Amy: Then take some echinacea, or St. John's Wort. Professor: Or a big fat placebo. It's all the same crap.

31st August 2006, 12:04 PM	#35
jskowron Really Bad at Karaoke Join Date: Jun 2005 Location: Massachusetts Posts: 112	Even assuming the physics/math were correct, the CT logic would still be along the lines of "since two outrageously huge automobiles crashing into each other would have this velocity......the government must have blown up the WTC buildings" They resort to physics/math to appear to be more of an authority than they are, and to introduce a strawman (e.g. "your book physics can't perfectly explain the ultra-complex, real world, probably never before thought of collapse of giant skyscrapers that have been hit by jets, and since it is unlikely that "physics" is wrong, the official explanation of what happened must be.")

31st August 2006, 02:24 PM	#36
Arkan_Wolfshade Philosopher Join Date: Jan 2006 Location: Making Mytheon come to life Posts: 7,158	Originally Posted by Arkan_Wolfshade fwiw, from a good friend of mine who is an ME at Bridgestone/Firestone Minor correction has been passed along to me: Quote: Well, if you use this in a post, I made a typo. Momentum = Mass * Velocity. So its MV = MV, not MoV = M0V. I was overzealous typing out my Mo's. As always, transparency is the best policy.
	__________________ Amy: You should try homeopathic medicine, Bender. Try some zinc. Bender: I am forty percent zinc. Amy: Then take some echinacea, or St. John's Wort. Professor: Or a big fat placebo. It's all the same crap.

31st August 2006, 03:14 PM	#37
Verde Muse Join Date: Mar 2006 Location: Where the jackalopes roam. Posts: 817	Originally Posted by boooeee If England changed it's driving laws such that everybody had to drive on the right side of the road, would the day get shorter, longer, or stay the same? As I recall, the actual discussion about this had the buses and lorries moving over first as a test period, and if successful the cars would change over the following month.