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[Samael]

Ya see, here's the way it works:

Why is the blue whale, the largest animal that's ever lived on this planet, incapable of eating anything larger than plankton?

Answer: Because that's the way it is.

Sometimes, that's just got to be good enough.

 

[Ultimate]

But to get back to the smooth vs. coarse question, atomic and molecular distances are so small that fine grind vs. coarse grind doesn't enter into it.

This is the bottom line. But it's still fun to think about

 

[knarfeng]

We're gonna get to the bottom of this one

No we are not. The subject is too complex to be worked out in words. And I, for one, do not have the equations for it.

 

[jgloveracob]

True enough, the atoms themselves don't touch. But it is still the atoms doing the pushing. The most you can say is that it's the electron cloud that is held together by the atoms. So, you still need to look at the molecular bond strengths (bond strengths between atoms).

Interactions between solids is PhD level stuff. Because to understand the interactions you have to look at molecular orbital energies of electrons. This is far more complex than studying atomic orbital energies. If you really want to pursue this, get a PhD in Physical Chemistry. It's that complex.

But to get back to the smooth vs. coarse question, atomic and molecular distances are so small that fine grind vs. coarse grind doesn't enter into it.

Aha, I see.

 

[riderV3]

The way I see it the electrons are concentrated in a thin V which repels a very thin spot breaking the bonds. Right?

Okay let's try this, I think I know what is confusing you.

Your teacher is correct, electrons don't touch, the only moment where electrons "touch"(not in a physical sense) each other is when there's a chemical reaction.

If the electrons on a blade don't repel the electrons on a fruit then what you have is a chemical reaction where a blade is literally "fused" with the fruit and you get a fruity balde.

But as you learned from the class, Electrons repel each other, that's why blade doesn't fuse with a fruit or whatever material it's cutting.

But that's as far as electrons go, they hold their place so blade is blade and fruit is fruit.
So while both objects busy retaining their chemical structure integrity it is physical pressure that splits the intermolecular forces that's holding the substance together.

So yes, electrons repel but not with enough force to split a chemical structure, it plays a part but what does the trick is the physical pressure.

 

[BA_Colt]

Google microtome.

 

[jgloveracob]

Okay let's try this, I think I know what is confusing you.

Your teacher is correct, electrons don't touch, the only moment where electrons "touch"(not in a physical sense) each other is when there's a chemical reaction.

If the electrons on a blade don't repel the electrons on a fruit then what you have is a chemical reaction where a blade is literally "fused" with the fruit and you get a fruity balde.

But as you learned from the class, Electrons repel each other, that's why blade doesn't fuse with a fruit or whatever material it's cutting.

But that's as far as electrons go, they hold their place so blade is blade and fruit is fruit.
So while both objects busy retaining their chemical structure integrity it is physical pressure that splits the intermolecular forces that's holding the substance together.

So yes, electrons repel but not with enough force to split a chemical structure, it plays a part but what does the trick is the physical pressure.

So the repelling keeps the knife and the material separate. I understand now.

 

[Nonprophet]

haha lessons:
1. Guys like to pick on each other, and do so relentlessly.
2. Opinions are like farts; everyone loves their own and just want to share, but anyone else's farts are just gross. :barf:

A basic summary of what I said...well without the farts. That's just gross!:jerkit:

 

[Nonprophet]

I'm just a chemist moonlighting as a materials engineer, so this is a bit out of my field, but I'll take a stab at it.



Because electrons alone are not what is holding the material together. You are actually dealing with molecular bonds between atoms. So you need to look at bond strengths. Metal cuts plastic because the metal is a crystal structure, while plastics are covalent bonds. The bond strengths in a crystal structure are greater than those of the covalently bonded plastic.

How this translates into super smooth vs. coarse edges is a bit farther than I am willing to guess. But electrons by themselves, it ain't.

Now there is a person who's word I'm taking as fact

 

[thombrogan]

Ps I'm only 15 And fresh out of chemistry class with a B.

Sorry, jgloveracob. I shouldn't have made my nonsense post in your thread and wouldn't have if I knew you were still in school. You've got an active mind and that's going to prove very useful. You also like to share what you know and doing so informs you of some things you don't already know. That's also going to be helpful, but it'll also get annoying at times like it was for you today.

With apologies,

Thom

 

[jgloveracob]

Sorry, jgloveracob. I shouldn't have made my nonsense post in your thread and wouldn't have if I knew you were still in school. You've got an active mind and that's going to prove very useful. You also like to share what you know and doing so informs you of some things you don't already know. That's also going to be helpful, but it'll also get annoying at times like it was for you today.

With apologies,

Thom

Don't worry about it. Today was a very bad day for me. I just brought my problems onto the forums.

 

[jimh0220]

Do you cut your pancakes via electron repulsion or with a knife? (Careful... trick question )

Dunno, but I do it with a fork.

 

[Ultimate]

Dunno, but I do it with a fork.

I use fork and knife to cut my pancakes into 8 equal triangles.

 

[GhostRing]

I use fork and knife to cut my pancakes into 8 equal triangles.

I cut mine into 6...there's no way I could eat 8.

 

[CrimsonTideShooter]

In my class we were told by the teacher that things never physically touch IE: finger on paper because the electrons would repel each other and have an atom sized gap between them. Thats where I got my theory/thought. Is this correct, if so why wouldn't it apply to knives

If two objects never actually touch then how does paint transfer from one car to the other in a collision?

I took all the chems. Learn it, take the test - then move on.

 

[jgloveracob]

If two objects never actually touch then how does paint transfer from one car to the other in a collision?

I took all the chems. Learn it, take the test - then move on.

I think its because the impact destroys the bonds and creates new ones. Dont quote me on that, not really sure.

 

[Guyon]

FACT: Honey badger just don't give a s...

oh wait, this isn't W&C.

 

[Samael]

More's the pity. If it was, we'd really be rockin' and rollin'.

 

[dsmegst]

Don't worry about it. Today was a very bad day for me. I just brought my problems onto the forums.

Don't mind the old farts around here. We really do like discussing knives, even when we talk it to death. Keep your eyes and ears open and you'll learn a lot, I sure am. :thumbup:

Now somebody explain the molecular science behind pancake syrup. The PhDs can start working on hot maple syrup and the side of bacon.

 

[Joshua J.]

An Iron atom is about 160 picometres across, though apparently they don't like each other that much and keep some extra space between them, making 250 pm per atom (or 248.2 according to these guys).
The thickness of an edge is determined by the scratch pattern of the sharpening material, the finest I've seen is half micron.

So, a half micron edge (air bleeding stupid sharp) would be 500 nanometres thick, at 4 atoms per nanometre you would have 2000 atoms in a half micron edge.
Do you think that 800 grit gives a nice fine edge? An 800 grit particle is 25 microns, or, 100,000 iron atoms thick.
(Here's a nice conversion table.)

All this is to say that I don't think the interaction between individual atoms has much to do with how a knife cuts.
The best example I can come up with, is that cutting paper is like crushing wood with a hydraulic press. Apply enough pressure and the weaker material will give way.