# Compressability and vibration

1. Jun 9, 2004

### one_raven

Imagine you have a perfectly dense incompressible fundamental particle.
Strike that particle with another of the same type.
Will they vibrate?

If something is not compressible. then I don't see how there could be any sort of shockwave that would cause the particle to vibrate.
Am I correct in this assumption?

Thanks

2. Jun 10, 2004

### Gokul43201

Staff Emeritus
Do you really mean "fundamental particle " ? Do you know what a fundamental particle is and what is involved in "striking that particle with another of the same type" ?

Forget about vibrate - which anyway, doesn't make much sense - they might not even be deviated.

This question is very fundamentally ill-posed. What does "perfectly dense " mean ? I believe you are making several assumtions here that are wrong.

If two billiard balls strike each other, there will be vibrations inside each ball (fundamental particles, on the other hand, have no internal structure), but the balls themselves don't exhibit oscillatory motion.

Rewrite your question, avoiding or explaining unclear terms.

3. Jun 10, 2004

### one_raven

As far as I understand it, a fundamental particle is one that is not made up smaller components. One that can not be broken down any further. The only particle(s) that is/are truly "solid".

Yes. A little imagination. That doesn't sound very difficult, but maybe that's just me.

Sorry, I didn't know a technical term for it.
What I meant was ideally solid, no space between the matter at all, no crystaline structure, no internal voids at all regardless of the size, unable to be compressed any further by any means. Does that make more sense?

Like what?

Forget the word "fundamental" if it is throwing you off.
Picture two fist-sized balls of matter if you want to.
What is important is that the balls are singular particles (can not be broken down further into distinct parts), are incompressible and are ideal solids.
I am trying to determine what will happen if the two particles strike each other.
If they are incompressible, I don't see how thay can store or transfer any kinetic energy.
What happens?

4. Jun 10, 2004

### Gokul43201

Staff Emeritus
Realize that you should not try to think of fundamental particles classically. It is because of deviations from classical behavior that "tiny things" are explained using quantum mechanics. If you took real fundamental particles and chucked them at each other, you could see:
a) the particles pass through each other and continue on their way, seemingly unaffected (the way ghosts move through walls) or
b) there is an interaction between the particles, causing them to swerve away from or into each other.
This is only a simplistic explanation (there are so many unforgivables uttered in this description, that it should not be considered a true QM description, just an illustration to highlight the non-classical behavior)

Now in the fist sized ball model, there are a few problems. It is still not clear what you mean by vibrate. You are correct, in that if the balls have no internal structure, then there cannot be vibrations inside them. The balls themselves will not vibrate about any mean position simply because there is no reason for that to happen. What makes the balls interact with each other ? Try and understand what vibrations are, why a central force/field is needed to have vibrations and how macroscopic forces are really just electrostatic repulsions between molecules.

The essence of your problem is in understanding how the particles interact with each other. And that depends on the nature of the particles.

Last edited: Jun 10, 2004
5. Jun 11, 2004

### Staff: Mentor

The term "solid" does not apply below a molecular level. Think about it: how do you know if a single atom is a solid, liquid or gas without seeing how its connected to the atoms around it? For the hypothetical:
You are of course correct. But then again, if I were Santa Claus, would I be fat? Just be careful about attaching any significance to the implications of an unrealistic hypothetical. And like Goku said - the rules in physics apply well to a baseball don't apply well to an atom or smaller - try to avoid thinking about very small things (quantum scale) in the same terms as very big things(classical scale).

Last edited: Jun 11, 2004