Outside energy had to be introduced for the twin towers to collapse the way they did

reply to post by Joey Canoli

Which explains your woeful belief that a body at rest is accelerating at 9.8m/s/s

A body's acceleration is the function of the BALANCE of forces acting on it.

A stationary body is being accelerated at 9.8m/s^2 towards the earth and being decelerated at 9.8m/s^2 in the opposite direction by the normal force.

I believe I was quite careful with my wording in referring to it as "the force required to" accelerate a body at 9.8m/s^2.

The force in the equation f=ma is the NET of forces acting on a body. Being stationary means it is being subjected to zero NET force, not zero force.

Gravity
Electromagnetism
Weak force
Strong force

All these are acting on the stationary object AT ALL TIMES.

Come on!! This is REALLLLLY basic stuff.

Originally posted by Darkwing01


A body's acceleration is the function of the BALANCE of forces acting on it.

Do you agree then thati if the balance of acceleration forces for a body at rest is zero, therefore when we solve for a body at rest:

0=m*0

Is correct?

Originally posted by Darkwing01
hyperphysics.phy-astr.gsu.edu...

What is the problem here PLB, what term in the equation is the one we are trying to establish?

Even though the application of conservation of energy to a falling object allows us to predict its impact velocity and kinetic energy, we cannot predict its impact force without knowing how far it travels after impact.

In other words, this equation cannot be solved on the basis you are trying to solve it.

As usual, you completely fail to read what I write, since I wrote "and a resulting 'a' determined by the distance this mass is tried to be stopped in.". Oh my, exactly the same as that link of yours is saying.

At the MOMENT OF IMPACT the objects have not moved at all, we are trying to establish what the value of the resistance is.

What I am saying is that the resistance must be at least 9.8m/s^2, so the object will decelerate. You impact force calculator in no way contradicts that.

And I am demonstrating that you are completely wrong, and don't even grasp the surface of the involved physics. For starters, resistance is not an entity expressed in m/s^2. What you are saying doesn't even make any sense.

The additional force can only come from the change in kinetic energy, which is exactly what we have been trying to get through to you.

Note that the above calculation of impact force is accurate only if the height h includes the stopping distance, since the process of penetration is further decreasing its gravitational potential energy.

We WANT TO KNOW what the stopping distance is.

Impact is not a "real force" like gravity is, it is just an extension of the normal force.

You are slowly going in the right direction, starting to grasp what impact forces are. How they are dependent on impact velocity, load capacity and the distance traveled through the resistance. Now you still need to figure out how gravity doesn't play a role in it, except for giving the mass its velocity.

What an absolutely fascinating (albeit one-sided) debate - great chaps, keep at it!

I particularly liked the red truck versus the scooter analogy but it appears that even that wasn't basic enough for the OSers.
How they can wallow in pseudo physics when they can't even comprehend the principles is beyond me - no wonder that the Israeli Government (with US Government backing) has got away with this ultimate act of inhumanity for the last ten years.

Although I'm going slightly off-topic, another 911 scenario was recently given to me, this time regarding the planes hitting the twin towers.
When people are asked to reverse the reality of what actually happened and imagine a huge steel-reinforced 100+ storey building flying through the air at 500 mph and hitting a parked thin-skinned jet airliner, EVERY time they say that the plane would be completey crushed leaving barely a scratch on the building.
So how did the planes on 911 manage to punch their way through as if the steel was butter when it's EXACTLY the same thing?

Surely another case of outside energy being introduced (that is if the planes weren't really missiles!).

Keep at it chaps, I'll be watching from the sidelines to see who loses steam first.

Originally posted by samuisteve
When people are asked to reverse the reality of what actually happened and imagine a huge steel-reinforced 100+ storey building flying through the air at 500 mph and hitting a parked thin-skinned jet airliner, EVERY time they say that the plane would be completey crushed leaving barely a scratch on the building.
So how did the planes on 911 manage to punch their way through as if the steel was butter when it's EXACTLY the same thing?

Surely another case of outside energy being introduced (that is if the planes weren't really missiles!).

Keep at it chaps, I'll be watching from the sidelines to see who loses steam first.

Big beats small, right? Imagine my comparatively small fist coming at your larger face at 100 MPH.

Who do you think is going down out of the two of us?

Now imagine a pin on the table face up. Now imagine your hand coming down onto it at speed. Now who comes off worst?

Your simplistic analogies are absurd as evidence of any kind.

Have you guys never seen the picture of a piece of straw piercing a tree stump due to the speed it was traveling at in a storm?

reply to post by humphreysjim


Ha ha!
Oh I love arguing with people who have 'limited' abilities of comprehension - the only trouble is that you can never 'win', as winning would mean teaching them things that are beyond them.
A bit like me being told the mysteries of the universe - ha ha!

Right.
Let's imagine that the hand you're hitting me with speed is made of aluminium tube and that my stationary face is steel reinforced. Hope you can write with your other hand.

(This is BRILLIANT fun - beats taking sweets off of babies!)

reply to post by Joey Canoli

0=m*0

Is correct?

No.

That is why the force exerted by gravity is equivalent to that required to accelerate the body at 9.8m/s^2 at all times, whether the object is actually moving or not.

VELOCITY IS NOT A TERM IN THIS EQUATION!

F=m*9.8
Let m = 10kg then F=98N WHETHER THE OBJECT IS MOVING OR NOT.

The fact that the object ONLY means that the normal force is 98N acting in the opposite direction, the force vector attributable to gravity is 10*9.8, not 10*0.

The normal force comes into existence when resistance is given (although it is really just an expression of mostly the effects of the electromagnetic force), but gravity is always acting.

If you have a cup on a table is there no gravity acting on it? Your interpretation implies exactly that. If gravity is exerting a force on the cup to keep it from floating away the acceleration CANNOT be zero.

You are confusing the net force with the individual force vectors.

www.physicsclassroom.com...
physuna.phs.uc.edu...

You're only proving how dumb using such simplistic thought examples is.

If we were to take it further, we'd have to shape my hand like a plane, fill it with jet fuel, and up the speed to levels I could never dream of reaching. Then, structure your face in the same way as the WTC, and...well, you get my point.

Basically, you can't do the actual math, and you don't know the actual physics involved because you're an arrogant armchair simpleton, so instead you resort to childlike thought experiments which prove nothing.

Originally posted by humphreysjim
You're only proving how dumb using such simplistic thought examples is.

If we were to take it further, we'd have to shape my hand like a plane, fill it with jet fuel, and up the speed to levels I could never dream of reaching. Then, structure your face in the same way as the WTC, and...well, you get my point.

Basically, you can't do the actual math, and you don't know the actual physics involved because you're an arrogant armchair simpleton, so instead you resort to childlike thought experiments which prove nothing.

Yes of course.
Whatever makes you happy.
ONE day you'll learn (maybe).

reply to post by samuisteve

So how did the planes on 911 manage to punch their way through as if the steel was butter when it's EXACTLY the same thing?

That isn't much of a mystery, though OS'ers never supply the correct solution.

The plane isn't cutting the tower perimeter, it is simply pushing it, causing it to shear. This isn't a question of hardness but one of density (the reason they use depleted uranium in anti-tank shells)

As the plane compresses against the walls its average density exceeds the density of the steel perimeter, meaning that it is less likely to be compressed than the wall is. The same goes for the incompressible fluid in the wing tanks.

Not much of a mystery at all tbh.

Originally posted by samuisteve

Originally posted by humphreysjim
You're only proving how dumb using such simplistic thought examples is.

If we were to take it further, we'd have to shape my hand like a plane, fill it with jet fuel, and up the speed to levels I could never dream of reaching. Then, structure your face in the same way as the WTC, and...well, you get my point.

Basically, you can't do the actual math, and you don't know the actual physics involved because you're an arrogant armchair simpleton, so instead you resort to childlike thought experiments which prove nothing.

Yes of course.
Whatever makes you happy.
ONE day you'll learn (maybe).

Apparently, even truthers don't agree with your thought experiments.

reply to post by -PLB-

Take a plate, and put a brick on it and wait for an hour. Then pick up the brick 50cm and let it drop on the plate. What? The same plate that has been resisting the brick over an hour now fails . Is it magic?

ok, lets do the same drop test, but with accurately scaled down materials, as the brick in your scenario is more durable AND weighs considerably more than the plate it is crushing.

lets make every 10 stories a brick, so that's 11 bricks. now, take three of those bricks and drop it on the other 8. for your "scenario" to be accurate, 3/4 or more of the towers would have fallen on 1/4 of the towers, and the bottom 1/4 is made of glass.

top material=bottom material. if you have some spare plates, do it all with plates and cement them together, then drop three on eight and tell me what happens. i guarantee you the top three break before the first four they collide with. no matter how high you drop it from, assuming the same durability, the one falling can only destroy its equal weight before itself is destroyed. then, energy will be lost, and mass will be lost.

the falling object cannot BOTH impart energy AND gain energy. so, those falling floors could not both destroy the ones below, AND continue.

Originally posted by Bob Sholtz
ok, lets do the same drop test, but with accurately scaled down materials, as the brick in your scenario is more durable AND weighs considerably more than the plate it is crushing.

Ok....

lets make every 10 stories a brick, so that's 11 bricks. now, take three of those bricks and drop it on the other 8. for your "scenario" to be accurate, 3/4 or more of the towers would have fallen on 1/4 of the towers, and the bottom 1/4 is made of glass.

So according to you, a brick accurately models 10 floors of the WTC. Do you really think so?

top material=bottom material. if you have some spare plates, do it all with plates and cement them together, then drop three on eight and tell me what happens. i guarantee you the top three break before the first four they collide with. no matter how high you drop it from, assuming the same durability, the one falling can only destroy its equal weight before itself is destroyed. then, energy will be lost, and mass will be lost.

the falling object cannot BOTH impart energy AND gain energy. so, those falling floors could not both destroy the ones below, AND continue.

When you are using such completely flawed analogies, its no wonder you don't understand it. Well, at least your are not using cardboard boxes in your analogy, like a prominent truther is doing.

I wonder if I should write again about the mass of the already failed floors between the top and lower section, causing the lower floors to fail. But I just realized its pointless.

reply to post by -PLB-


i'm sorry, but arguing that a brick falling on a plate is more accurate than me taking into account every floor(different materials, thicknesses completely off. i mean, you're saying a plate is equal to 90 stories, and a brick that's at least 6 times thicker is 20 stories. weight completely off), mine are to proportion and consistant. and fyi, heat rises, and the jet impacted wtc 1 at floor 92-98. i included the WHOLE fire damaged area as falling and not damaged AND still added space for it to fall, so very heavily erring on the side of the OS.

it's still bunk.

concrete mason blocks would demonstrate this best, and if i find enough, i'll make a video.

reply to post by Bob Sholtz


I nowhere said that a brick falling on a plate is an accurate model or analogy of the WTC collapses. I used it to demonstrate a certain physical effect; that an object that can hold a certain mass can be completely crushed by that same mass. I also explained with decent detail how this can happen without any deceleration taking place. However, with my explanations I am of course just casting pearls before swine.

reply to post by humphreysjim


if you punched a skull at 100 mph, yes, the person would die, but every bone in your fist would shatter. a more apt analogy would be for you to punch the fist of a 200 lb boxer, you punch as hard as you can, and he'll punch as hard as he can. put your hand where your mouth is =P

a needle is generally going to be steel, where a fist is soft tissue, but i assure you, you impart equal energy to it as it does to you.

try shooting a bullet against a 1" thick lead bar, and tell me which wins.

your analogies purposely ignore an important caveat, big thing versus small thing made of similar materials with similar durability. the twin towers also had equal surface area when the top impacted the bottom.

you are either being ignorant of these important caveats, or willfully ignorant. judging by how you've been posting, i'd go with the latter.

reply to post by -PLB-

I nowhere said that a brick falling on a plate is an accurate model or analogy of the WTC collapses.

you implied that it was evidence of the towers collapsing as they did without resistance being removed. and yes, the brick would lose momentum equal to the amount the plate absorbed. drop the plate on the brick, and tell me if the brick shatters.

you're pretty good at twisting words, but anyone who knows a thing or two about logic sees through you.

Originally posted by PLB

This is wrong. An object falling 1 meter will have a much greater impact force than an object falling 10 meter

But the thing you keep missing is that the impact force is still the SAME for both objects, regardless of how far the falling object is dropped, or what it's velocity is, equal opposite reaction, forces always come in pairs.

So if the force is equal on both objects, regardless of velocity, it means MASS is what determines what is damaged not the velocity.

This is why I posted the bug red truck and scooter example, and the bug hitting the windshield question, that you failed to understand contradicts what you are claiming.

Originally posted by Bob Sholtzyour analogies purposely ignore an important caveat, big thing versus small thing made of similar materials with similar durability. the twin towers also had equal surface area when the top impacted the bottom.

Do you not realize how silly you're being with your own analogies?

www.fallacyfiles.org...

"Some arguments from analogy are based on analogies that are so weak that the argument is too weak for the purpose to which it is put. How strong an argument needs to be depends upon the context in which it occurs, and the use that it is intended to serve."

If you're going to try to refute the possibility of the collapse of the WTC without explosives, you're going to have to do far better than weak analogies, thought experiments, and silly "big thing beats little thing" statements which would have you laughed out of any serious discussion with experts.

That's my reason for replying with a weak analogy of my own. Your analogies are just as lame as mine, because no analogy or thought experiment is going to be sufficient to tackle such a complex problem as the collapse of the towers. That's why structural engineers and physicists have written pages of formulas attempting to explain what happened on that day and how, which still fall way short of the mark because we are missing so much key information about the precise nature of the damage the building had taken at that very time. So many factors, "big thing beats little thing" doesn't cut it, I'm afraid.