If it doesn't agree with experiment, it's wrong. Part II

[Slowvehicle]

No, it's the same mistake you keep making, you keep on conflicting which Force pairs are to be used. The Normal Force is NOT the opposite force of Gravity, and the force applied by the floors in the collapse are not the opposite force to gravity either. When you finally understand this, you might start to understand where you are going wrong.

I'm going to use some pictures to show you were you are going wrong.

When an object sits on a surface we are actually dealing with THREE forces and THREE reactive forces. In the Illustrations below I have labeled the pairs so that (+) is the force, and (-) is the counter force.

This is our object sitting on a surface on level ground. Our Three Forces are G for Gravity, N for normal, and F for Parallel Force and Friction. The three counter forces are also shown.

G⁺ is the force of gravity pulling the object downwards to the Centre of Mass (CoM) of the Earth. G^- is the Building pulling the Earth upwards to its CoM. These are matched pairs.

The Normal Force is created as N with N⁺ the weight of the building pushing the surface downwards towards the Earth's CoM. N^- is the surface pushing the building back upwards. These are a matched pair.

Finally we have Sideways Forces. This is any force, or force component, that is parallel to the surface. It will have a matching force opposing it, this is what we call friction.

We can Illustrate these three forces below.

[qimg]http://www.internationalskeptics.com/forums/picture.php?albumid=1203&pictureid=10663[/qimg]

Now, yes, in this scenario the Force N⁺ is of the same magnitude as G⁺ and the reactive forces G^- and N^- are likewise the same magnitude. But N and G are not pairs. Rather N⁺ + F⁺ = G⁺ and N^- + F^- = G^-
The Magnitude of G only equals the magnitude of N because the magnitude of F = 0.

We can illustrate this by tilting the entire experiment by 10 degrees

[qimg]http://www.internationalskeptics.com/forums/picture.php?albumid=1203&pictureid=10664[/qimg]

Now we can clearly see that the Normal Force does not equal the Gravitational Force in either direction or magnitude. We still have our three pairs, but now because N only cancels out a part of G, F now has both a magnitude and a direction as well.

Now obviously if we continue to rotate the surface, at a certain point, F- is going to reach a maximum value that it can apply as a reactive force. At that point, our object will slide because N + F < G and as a result we will get acceleration. This again proves that the Normal Force is not the equal and opposite reaction to Gravity.

 

[AZCat]

You are playing the semantics game, and you have written a whole lot of meaningless stuff to try to make a simple issue more complicated.

At the instant of impact the acceleration changes. Acceleration changes because there is a force exerted that is in the opposite direction of the original acceleration. When an accelerating object experiences an acceleration in the opposite direction we say it decelerates.
Again, you are trying to complicate something that does not need to be.

Shades of Tony Szamboti here...

 

[PhantomWolf]

When an accelerating object experiences an acceleration in the opposite direction we say it decelerates.

This is incorrect. An object decelerates when it experiences a negative acceleration. If it is accelerating then any acceleration in the opposite direction much be greater than the acceleration it is undergoing when it meets the acceleration in the opposing direction.

In other words..

Deceleration only occurs when A^- > A⁺
This is because we must add the two accelerations together so as long as A⁺ is greater than A^-, the object will have a positive acceleration, and thus still be accelerating.

 

[DaveThomasNMSR]

You are playing the semantics game, and you have written a whole lot of meaningless stuff to try to make a simple issue more complicated.

At the instant of impact the acceleration changes. Acceleration changes because there is a force exerted that is in the opposite direction of the original acceleration. When an accelerating object experiences an acceleration in the opposite direction we say it decelerates.

Again, you are trying to complicate something that does not need to be.

Again, you are simply Wrong. This time, about deceleration.

PhD. physics teacher Richard Cardenas (15 years) says the following:

Deceleration is the term used for acceleration that causes an object to slow down

Note that this agrees exactly with what Redwood was saying, and which you could not understand, dismissing it as "a whole lot of meaningless stuff ":

When you drop a brick, da/dt=0, but when it breaks through a piece of tissue paper, da/dt goes from zero to negative. This does not mean that the brick decelerates (dv/dt=negative). It merely experiences an interval where its acceleration was less than g.

Once again, FF, you are wrong. At least you are consistent.

 

[PhantomWolf]

Deceleration only occurs when A^- > A⁺

More pictures for you....

Here we have a 1kg ball in free fall, it is accelerating at g (9.8m/s²)

We are now going to apply an Acceleration (A) to it in the opposite direction of g (i.e. directly up.) This Acceleration is going to created at a force of 3 N, thus A will be 3 m/s².

To get the Ball's new Acceleration we need to add Vectors A and g

Since A is in the opposing direction to g we use it as negative, so...

-3 m/s² + 9.8 m/s² = 6.8 m/s²
Our ball is now accelerating at 6.8 m/s². Yes the rate of acceleration has decreased, but overall it is still accelerating.

Now let's apply a greater force, 12 N so that A = 12 m/s²

Again we add the two vectors together, treating the magnitude of A as negative.

-12 m/s² + 9.8 m/s² = -2.2 m/s²
This time because A is greater than g we get a negative acceleration, or a deceleration. Our ball will slow at 2.2 m/s²
As you can see, the ball will only decelerate if and when A > g.

 

[Redwood]

How? Please explain how the direction of net forces and similar sequences of net forces are dependent on scale. Please provide a link to a credible source that supports your opinion.

For the umpteenth time, nobody, but nobody has ever denied that the direction of any force depends on scale. But scale matters in modeling. I'm going to give you the benefit of the doubt and assume that you are simply too obtuse to understand this. But I'll give it one last try.

An elephant's legs can support more weight (a static force) than a squirrel's. But while a squirrel can easily leap 15 ft. out of a tree and absorb the impact (a dynamic force) and scamper away, if you drop an elephant dropped the same 15 ft. it breaks its legs and probably dies. The difference is scaling. Capisce?

If Cole "adequately displays Newton's laws", according to your [Seymour Butz] own statement, and one of the ways to "adequately display Newton's laws" was to remove the support columns with firecrackers, how on earth can you make the statement that this is not evidence of CD?

Everything "displays Newton's laws", from the motion of the planets about the sun (except for that pesky Planet Mercury ) to a video of my living room with everything lying motionless. A small child plopping herself down in a chair displays Newton's laws. A fat man plopping himself down in a chair, breaking it, displays Newton's laws. But Newton's laws don't explain WHY the chair broke under the fat man but not for the little girl. Other laws of physics must be resorted to.

The only way Cole replicated the observed motion during the collapse of WTC1 and WTC2 was to remove the support columns with firecrackers. No other experiment replicated the observed motion. How can anyone possibly claim that this does not support the theory of CD?

Because Cole is either so obtuse or so far gone in his conspiracism that he fails to understand scaling. (Or maybe he's just dishonest.) There are plenty of real life examples of progressive collapse. (See "Verinage", which works with real buildings. There's that scale thing again! ) Cole's inability to demonstrate progressive collapse is a reflection on Cole, not on reality.

 

[MikeG]

You're right. I will never modify my position, because I know I am right. I have provided links to credible sources that show I am right.

Well, I'm sorry*, but not surprised. You clearly came here to lecture us, and found yourself utterly out of your depth. You had two options: listen and learn, or put your fingers in your ears and shout "I know I'm right". You chose the wrong option.

* Only because a whole lot of intelligent and highly qualified people invested a lot of time in trying to help you.

Where you're wrong is that you assume I will keep playing the games that are going on here. That is not going to happen.

Where you're going wrong is thinking we're playing games. We're right. You're wrong, and there are no games involved.

When you stomp off declaring victory, will you repeat your wish that all our relatives die in the next terrorist attack, because some here didn't get to see it last time you did that? Maybe add in that bit about us all being paid shills (I had to look up "shill"). It really did make for a memorable flounce last time.

 

[Redwood]

Originally Posted by Redwood
Quick point, for the benefit of everyone, except FF, who couldn't possibly understand:

In kinematics, we have velocity, defined as change of position over time = dx/dt.

[much snipped for brevity]

You are playing the semantics game, and you have written a whole lot of meaningless stuff to try to make a simple issue more complicated.

False. It's quite meaningful, and your failure to understand it is an illustration of why you should be in school, learning, instead of here, commenting.

At the instant of impact the acceleration changes. Acceleration changes because there is a force exerted that is in the opposite direction of the original acceleration.

TRUE! Give that man a pizza!

When an accelerating object experiences an acceleration in the opposite direction we say it decelerates.

True again! But that's not what we're discussing! A falling brick is under constant acceleration due to gravity and when it (or any other weighty object) strikes something as insubstantial as tissue paper, the paper can't even slow it down, (i.e. make dv/dt negative)it can merely briefly reduce the acceleration to less than g (i.e. da/dt becomes negative) Something more substantial, like a pane of glass, will reduce the velocity (dv/dt becomes negative).

Again, you are trying to complicate something that does not need to be.

No, you are once again showing that you have no idea what you are talking about. More's the pity that you waste your time here when you could be studying and getting smarter.

I can follow this up with another, even better example, but I'm not in the business of instructing young'uns in physics, and I'm sure that you still won't get it.

 

[quadraginta]

We're in deep ****, guys. Weve been found out, and now every bridge and construct is coming to fall down immediately, if not sooner,

<snip>

Or float away. Which, you must admit, would be a lot more interesting.

 

[Redwood]

Originally Posted by Redwood
...But we can also have a change in acceleration (which may have a name somewhere, but I don't know what it is) = da/dt = dv/dt2 = dx/dt3...

It's called the "jerk". I am not kidding.

So, you're saying that Tony Sz's paper should have been titled, The Missing Jerk?

 

[Dave Rogers]

I see that there's a key difference between part I and part II of the thread. In part I, FF was claiming that Cole was simply demonstrating Newton's Laws and that these are scale invariant. He now seems to have changed his mind and is saying that Cole was replicating the motions of the towers. So when anyone points out that Cole's models weren't accurate representations of the towers, FF replies that they weren't meant to be, and when anyone points out that Cole and FF have misapplied Newton's Laws, FF replies that Cole's models prove that they're correctly applied to the towers. So FF's position requires, in fact demands, that Cole's models both are and are not intended to represent the actual behaviour of the towers, depending on which set of mental errors he's trying to deny.

Dave

 

[FalseFlag]

You are wrong. The force that the earth exerts upon the building, which is equal and opposite to the gravitational force the building exerts upon the earth, is called...

gravitational force.

You refuse to listen to me. Fine. The two sources I have linked say you are wrong. Actually, any credible source says you are wrong.

http://www.sparknotes.com/physics/dynamics/newtonapplications/section1.rhtml

The normal force can also be seen as a direct consequence of Newton's Third Law. Continuing with the example of the man on the platform, his weight, due to the gravitational force, pushes down on the platform. Newton's third law predicts that this force on the platform must be accompanied with an equal and opposite force applied to the man by the platform. This force is precisely the normal force.

https://www.khanacademy.org/science...ontact-force/v/normal-force-and-contact-force

If you want to continue to claim that you are right, please copy and paste the relevant text or point out where in the video your statement is confirmed.

I realize that no one will admit that I'm right. So, if you want to continue to play your game, from now on you are going to have to claim credible sources are not right.

 

[FalseFlag]

I see that there's a key difference between part I and part II of the thread. In part I, FF was claiming that Cole was simply demonstrating Newton's Laws and that these are scale invariant. He now seems to have changed his mind and is saying that Cole was replicating the motions of the towers. So when anyone points out that Cole's models weren't accurate representations of the towers, FF replies that they weren't meant to be, and when anyone points out that Cole and FF have misapplied Newton's Laws, FF replies that Cole's models prove that they're correctly applied to the towers. So FF's position requires, in fact demands, that Cole's models both are and are not intended to represent the actual behaviour of the towers, depending on which set of mental errors he's trying to deny.

Dave

1. The discussion about Newton's laws was to prove I understood them. That was a mistake because no one will ever admit I am correct.

2. After more than 2000 posts I realized that I would need to be as specific as possible when talking about Cole's video. It hasn't done any good because skeptics are still refusing to listen.

You also continue to misunderstand what Cole is trying to do. The very last statement in your post proves that. Cole is not trying to replicate the (structural) behavior of the towers. Cole is attempting to replicate the observed motions during the collapse. You are trying to get me to play the semantics game, and I will not play. Cole is demonstrating similar accelerations, similar directions of net force and similar sequences of net forces. If you are actually have a PhD in physics you would see this, and you would not continue to deny it.

 

[PhantomWolf]

You refuse to listen to me. Fine. The two sources I have linked say you are wrong. Actually, any credible source says you are wrong.

http://www.sparknotes.com/physics/dynamics/newtonapplications/section1.rhtml



https://www.khanacademy.org/science...ontact-force/v/normal-force-and-contact-force

If you want to continue to claim that you are right, please copy and paste the relevant text or point out where in the video your statement is confirmed.

I realize that no one will admit that I'm right. So, if you want to continue to play your game, from now on you are going to have to claim credible sources are not right.

More examples of googling without understanding.

 

[FalseFlag]

But that's not what we're discussing! A falling brick is under constant acceleration due to gravity and when it (or any other weighty object) strikes something as insubstantial as tissue paper, the paper can't even slow it down, (i.e. make dv/dt negative)it can merely briefly reduce the acceleration to less than g (i.e. da/dt becomes negative) Something more substantial, like a pane of glass, will reduce the velocity (dv/dt becomes negative).

Why are you contradicting yourself? You claim I'm right, but then you say the paper can't even slow the brick down. You are playing the semantics game. You admit that the rice paper will reduce the acceleration at the instant of impact. Why does it matter if the velocity won't substantially change? What are you trying to prove?

The following statement is true. An accelerating brick will exert a force on a piece of rice paper at the instant of impact. The piece of rice paper will exert an equal and opposite force on the brick. This equal and opposite force will cause the acceleration of the brick to change at the instant of impact. The magnitude of this force will be minute. A minute change in the acceleration of the brick will have a minute change in velocity of the brick.

Can we agree on that statement? If we can agree, please explain your point.

No, you are once again showing that you have no idea what you are talking about.

How can you say I'm right twice in one post and then say I have no idea what I'm talking about?

 

[FalseFlag]

More examples of googling without understanding.

Support your claim with proof. Provide a link to a credible source that proves I am wrong. Wait. Provide a link to a different credible source that proves the two credible sources I have posted are wrong.

 

[PhantomWolf]

Cole is not trying to replicate the (structural) behavior of the towers. Cole is attempting to replicate the observed motions during the collapse.

Which is pointless unless you also replicate the structure. Replicating the motion with a totally different structure only shows that you can replicate the motion with a different structure.

I can replicate the motion of a car wheel with a windmill sail, but that doesn't mean that the mechanics behind the two are the same.

Likewise showing similar motion with a totally different structure reveals nothing about the WTC and the mechanics of that collapse. This is Cole's problem, which is what you have been being told right from the start.

 

[FalseFlag]

For the umpteenth time, nobody, but nobody has ever denied that the direction of any force depends on scale.

Yes, they have.

But scale matters in modeling. I'm going to give you the benefit of the doubt and assume that you are simply too obtuse to understand this. But I'll give it one last try.

You are only proving that you refuse to accept what is true. You say that scale does not matter when talking about directions of net force, then, once you realize the implication of your statement, you try to obscure it with your modeling nonsense.

An elephant's legs can support more weight (a static force) than a squirrel's. But while a squirrel can easily leap 15 ft. out of a tree and absorb the impact (a dynamic force) and scamper away, if you drop an elephant dropped the same 15 ft. it breaks its legs and probably dies. The difference is scaling. Capisce?

Your example has nothing to do with Cole's experiments. Nothing. Not even a little.

Everything "displays Newton's laws", from the motion of the planets about the sun (except for that pesky Planet Mercury ) to a video of my living room with everything lying motionless. A small child plopping herself down in a chair displays Newton's laws. A fat man plopping himself down in a chair, breaking it, displays Newton's laws. But Newton's laws don't explain WHY the chair broke under the fat man but not for the little girl. Other laws of physics must be resorted to.

You have to be kidding. Yes, Newton's laws do explain why a chair might break when a larger man sits on it.

Newton's second law says F=ma. The larger man exerts a larger force on the chair, because the larger man has a larger mass. If a chair breaks, it can't support the force being exerted by the object it is trying to support.

 

[PhantomWolf]

Support your claim with proof. Provide a link to a credible source that proves I am wrong. Wait. Provide a link to a different credible source that proves the two credible sources I have posted are wrong.

You'll get to my prove soon enough I am sure, but it doesn't need a link, it needs you to actually understand what you read.

You fail to understand this part...

his weight, due to the gravitational force, pushes down on the platform.

You take this to mean that the force created by the weight pushing down is exactly the same force as that created by gravity pulling the man down.

It isn't. It is a force that is between the object and the surface. It is caused by gravitational force, but it is not gravitational force.

This force has its own pairing and only when the surface is perpendicular to Gravitational force will the Normal Force's magnitude equal the gravitational force's magnitude. As soon as we tilt the surface, they are no longer equal, and they are no longer in line with each other.

ETA: If I were to place you in a room attached to a large centrifuge and then run it so that it was producing the equivalent of 1 g, the normal force of your standing on the floor would be perpendicular to gravitational force, and would be created by the surface of the floor pushing up against your feet rather then gravity. They are two different forces.

 

[FalseFlag]

I can replicate the motion of a car wheel with a windmill sail, but that doesn't mean that the mechanics behind the two are the same.

You just proved Cole right. You CAN replicate the motion of a car wheel with a windmill sail.

Similar accelerations, similar directions of net force, and similar sequences of the net forces are not dependent on scale.

Will you stop arguing with me now? You just proved Cole is right.