Could somebody give me evidence that friction causes molten metal?

[BubbleGum]

Answer is yes.

Google 'friction welding'.

~Bub

Hey, that was my first post. And no one said 'Hi'.

It was a good one too... Steel is routinely melted via pure friction.

~Bub

 

[delphi_ote]

Hey, that was my first post. And no one said 'Hi'.

It was a good one too... Steel is routinely melted via pure friction.

~Bub

Hi.

Seriously, welcome! I didn't notice it was your first post.

 

[William Rea]

Ok, I'm going to think about this in more detail.

Are you saying that if I drop a golf ball into a sand trap, that not all of the gravitional energy is converted into heat? Some of it is used to do work on the earth?

That would mean, also, I am doing work on the earth, as well as the ball, when I lift the golfball out of the sand, then?

What happens, asymtotically, as I pick up and drop the golfball an infinite number of times to the trajectory of the earth? (Assuming it was traveling in a straight line, and not rotating). I presume it stays relatively straight... but does this mean if I lift the ball, and never drop it, I've deflected the earth's path?

Yes, the deflection of the earth will be infinitessimally small but the laws of conservation of energy and momentum apply depending upon the efficiency of the process. Dropping the ball into the sand would also disperse kinetic energy into the sand (hence a crater forms).

You do work on the ball by lifting it to a higher gravitational potential energy state. The energy for this is derived from chemical energy being converted to kinetic energy in your body. Although the mass of your body is applying a force to the earth you are in equilibrium and you are not changing your energy state relative to the earth therefore you are not doing work on the earth when lifting the ball.

If you lift the ball and never drop it you simply store the gravitational potential energy.

Dropping the ball is an energy conversion process, you do not destroy the energy (other than by losses) simply by dropping it. When the ball reaches reaches the earth's surface after falling all of the potential energy available is converted to kinetic energy.

 

[William Rea]

Ok, I'm going to think about this in more detail.

Are you saying that if I drop a golf ball into a sand trap, that not all of the gravitional energy is converted into heat? Some of it is used to do work on the earth?

That would mean, also, I am doing work on the earth, as well as the ball, when I lift the golfball out of the sand, then?

What happens, asymtotically, as I pick up and drop the golfball an infinite number of times to the trajectory of the earth? (Assuming it was traveling in a straight line, and not rotating). I presume it stays relatively straight... but does this mean if I lift the ball, and never drop it, I've deflected the earth's path?

Yes, the deflection of the earth will be infinitessimally small but the laws of conservation of energy and momentum apply depending upon the efficiency of the process. Dropping the ball into the sand would also disperse kinetic energy into the sand (hence a crater forms).

You do work on the ball by lifting it to a higher gravitational potential energy state. The energy for this is derived from chemical energy being converted to kinetic energy in your body. Although the mass of your body is applying a force to the earth you are in equilibrium and you are not changing your energy state relative to the earth therefore you are not doing work on the earth when lifting the ball.

If you lift the ball and never drop it you simply store the gravitational potential energy.

Dropping the ball is an energy conversion process, you do not destroy the energy (other than by losses) simply by dropping it. When the ball reaches the earth's surface after falling, all of the potential energy available is converted to kinetic energy.

 

[Shrinker]

Yes, the deflection of the earth will be infinitessimally small but the laws of conservation of energy and momentum apply depending upon the efficiency of the process. Dropping the ball into the sand would also disperse kinetic energy into the sand (hence a crater forms).

You do work on the ball by lifting it to a higher gravitational potential energy state. The energy for this is derived from chemical energy being converted to kinetic energy in your body. Although the mass of your body is applying a force to the earth you are in equilibrium and you are not changing your energy state relative to the earth therefore you are not doing work on the earth when lifting the ball.

If you lift the ball and never drop it you simply store the gravitational potential energy.

Dropping the ball is an energy conversion process, you do not destroy the energy (other than by losses) simply by dropping it. When the ball reaches the earth's surface after falling, all of the potential energy available is converted to kinetic energy.

Wait a minute. When the the structures keeping the WTC and the earth apart failed, the WTC fell to earth, but the earth also fell towards the WTC (a tiny tiny amount). When the two met, both stopped moving. The KE of the earth and the towers was used 100% for destructive work. No?

The idea that an earth-bound object can push the earth is like saying you can power a yacht by installing a fan on the back and blowing it at the sails.

Am willing to be shown wrong...

 

[William Rea]

Wait a minute. When the the structures keeping the WTC and the earth apart failed, the WTC fell to earth, but the earth also fell towards the WTC (a tiny tiny amount). When the two met, both stopped moving. The KE of the earth and the towers was used 100% for destructive work. No?

The idea that an earth-bound object can push the earth is like saying you can power a yacht by installing a fan on the back and blowing it at the sails.

Am willing to be shown wrong...

Take 2 snooker balls, keep one stationary and then roll the other into it.

 

[William Rea]

Wait a minute. When the the structures keeping the WTC and the earth apart failed, the WTC fell to earth, but the earth also fell towards the WTC (a tiny tiny amount). When the two met, both stopped moving. The KE of the earth and the towers was used 100% for destructive work. No?

The idea that an earth-bound object can push the earth is like saying you can power a yacht by installing a fan on the back and blowing it at the sails.

Am willing to be shown wrong...

On the same level as my point about the Earth moving you are right that as soon as the tower became essentially a free body the graviational force between them would cause attraction and they would move closer by an infinitessimally small amount.

Arguing that the Earth fell towards the tower would I guess come down to the point of reference. Someone standing on the tower could observe that the Earth is falling on him. As I said in the post conventionally the PE would be relative to a reference point on the Earth's surface.

It was the point of my illustration that not all the available KE did destructive work to collapse the tower. Some of it was lost into the Earth itself and some was not in a form useful to do work.

The point is that the tower was not Earth "bound" when it collapsed.

Incidentally, for every force there is an equal and opposite reaction. If you attached a fan to the yacht it would propel it simply because it causes a force, the sail would not be required. In the same way we don't need to put something solid behind a jet engine to make it propel us forward.

 

[gumboot]

I keep hearing that the molten metal at wtc was caused by friction.

I have never heard of this phenomenon and if true would be very interested to see the proof of this.

Proof that friction can cause molten metal? It's in the words themselves:

Friction:

In situations where the surfaces in contact are moving relative to each other, the friction between the two objects converts kinetic energy into heat.
Source

Molten:

In physics, melting is the process of heating a solid substance to a point (called the melting point) where it turns liquid. An object that has melted is molten.
Source

Friction generate heat. Sufficient heat increases a solid's temperature until it reaches melting point and turns into a a liquid.

So yes, friction can produce molten metal.

Someone mentioned this was high school level physics. I beg to differ. This is primary school level science. I'm not sure what it is called in the US. I recall learning about melting and freezing when I was about 5.

-Gumboot

 

[gumboot]

The idea that an earth-bound object can push the earth is like saying you can power a yacht by installing a fan on the back and blowing it at the sails.

That only works if the sail in question happens to be a spinnaker...

-Gumboot

 

[William Rea]

Proof that friction can cause molten metal? It's in the words themselves...Friction generate heat. Sufficient heat increases a solid's temperature until it reaches melting point and turns into a a liquid...Someone mentioned this was high school level physics. I beg to differ. This is primary school level science. I'm not sure what it is called in the US. I recall learning about melting and freezing when I was about 5.

-Gumboot

In fact depending on the composition, most alloys have a liquidus and solidus with zones in between that are mushy.

Materials also have a latent energy requirement to change between states so the melting process would not be a simple linear heat energy to raise the temperature.

It is fact that friction can cause melting but I still remain skeptical that there would be enough "useful" energy available during collapse to cause molten pools of steel.

 

[defaultdotxbe]

It is fact that friction can cause melting but I still remain skeptical that there would be enough "useful" energy available during collapse to cause molten pools of steel.

i dont think there was enough to create pools of molten steel, of course i dont think there were any pools of molten steel either, lol

 

[Gravy]

Incidentally, for every force there is an equal and opposite reaction. If you attached a fan to the yacht it would propel it simply because it causes a force, the sail would not be required.

True, but yachts are harder to steer in reverse.

 

[alfaniner]

fyi - pdoherty has been banned. That was totally unexpected.

 

[defaultdotxbe]

fyi - pdoherty has been banned. That was totally unexpected.

i understand he created a ne account to get around a 3 day suspension

although i dont know what the suspension was for

 

[gumboot]

It is fact that friction can cause melting but I still remain skeptical that there would be enough "useful" energy available during collapse to cause molten pools of steel.

I would be surprised if anyone here believed friction from the WTC collapse produced pools of molten steel.

-Gumboot

 

[TjW]

I would be surprised if anyone here believed friction from the WTC collapse produced pools of molten steel.

-Gumboot

But it probably could supply enough heat to set fire to pdoherty's strawman.

 

[Shrinker]

On the same level as my point about the Earth moving you are right that as soon as the tower became essentially a free body the graviational force between them would cause attraction and they would move closer by an infinitessimally small amount.

Arguing that the Earth fell towards the tower would I guess come down to the point of reference. Someone standing on the tower could observe that the Earth is falling on him. As I said in the post conventionally the PE would be relative to a reference point on the Earth's surface.

It was the point of my illustration that not all the available KE did destructive work to collapse the tower. Some of it was lost into the Earth itself and some was not in a form useful to do work.

The point is that the tower was not Earth "bound" when it collapsed.

Incidentally, for every force there is an equal and opposite reaction. If you attached a fan to the yacht it would propel it simply because it causes a force, the sail would not be required. In the same way we don't need to put something solid behind a jet engine to make it propel us forward.

Your snooker ball analogy is plain wrong. If I jump up and down enough times during the night will I push the earth closer to the sun? No.

If you fire a canonball up into the air, the recoil will push the earth backwards, yes? When the canon ball comes back down, will the impact push the earth backwards as well? Will you get two pushes for the price of one? If it does, you're well on your way to building a perpetual motion machine. Good luck with that.

Building the WTC pushed the bulk of the planet 'downwards' relative to the earth's centre of gravity. When the WTC fell, the earth came back up again. The centre of gravity of (earth+WTC) never moved at all. All of the PE was used to deform the earth and the towers during the collision.

 

[Anti-sophist]

All of the PE was used to deform the earth and the towers during the collision.

I thought that, as well. This conversation is bringing up memories of my classes on statics and dynamics. Even simple questions involve deep thought.

 

[Brainache]

I'd like to take this opportunity to wish pdoherty a happy birthday. It's a shame he can't be with us to share the occasion. We could have had cake.

 

[William Rea]

Your snooker ball analogy is plain wrong. If I jump up and down enough times during the night will I push the earth closer to the sun? No.

If you fire a canonball up into the air, the recoil will push the earth backwards, yes? When the canon ball comes back down, will the impact push the earth backwards as well? Will you get two pushes for the price of one? If it does, you're well on your way to building a perpetual motion machine. Good luck with that.

Building the WTC pushed the bulk of the planet 'downwards' relative to the earth's centre of gravity. When the WTC fell, the earth came back up again. The centre of gravity of (earth+WTC) never moved at all. All of the PE was used to deform the earth and the towers during the collision.

My snooker ball analogy is plain right. When 2 free bodies like snooker balls collide energy is transferred.

If you fire a cannonball in the air you change Chemical Energy into Heat Energy and then KE energy. Some of the KE is lost in the recoil the rest is converted into PE as the ball climbs which is then released as KE until the cannonball hits the ground and transfers the remaining KE energy into the Earth. Yes you get two backwards pushes but not for free, the Chemical Energy is finally lost in a form that is not available to do work. It is nowhere near a perpetual motion scenario.

Chemical Energy conversion into KE into PE was used to raise the WTC, it was constructed in equilibrium and not fired into the air (as far as I know) so no reaction due to imbalance in forces was created. as soon as the tower became a free body the PE was released. The centre of gravity of the Earth would have been moved by an infinitessimally small amount by adding the WTC due to the moment change.

Your last sentence is close though.