| Topic: |
Science > Physics |
| User: |
"" |
| Date: |
08 Mar 2006 05:12:24 PM |
| Object: |
Where does the spring force come from? |
We know that atoms are held together by atomic bonds and when one atom
is moved away from the one it's bonded to, there is a restorative force
that 'pulls' it back. But how can we explain the nature of this force
in terms of the electrostatic/electromagnetic forces between charged
atomic particles (proton & electron)? In a covalent bond an electron is
shared between two atoms (i.e. its wavefunction is spread over a wider
area), but how does that explain the restorative force? If I move one
atom away from another, I'm moving the positively charged nucleus away
from this shared electron, so the electrostatic force between the
nucleus and the electron should only get smaller, not larger (as
hooke's law predicts).
Brian
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| User: "Spaceman" |
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| Title: Re: Where does the spring force come from? |
08 Mar 2006 06:44:23 PM |
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<vze2vt56@verizon.net> wrote in message
news:1141859544.660278.266010@e56g2000cwe.googlegroups.com...
We know that atoms are held together by atomic bonds and when one atom
is moved away from the one it's bonded to, there is a restorative force
that 'pulls' it back. But how can we explain the nature of this force
in terms of the electrostatic/electromagnetic forces between charged
atomic particles (proton & electron)? In a covalent bond an electron is
shared between two atoms (i.e. its wavefunction is spread over a wider
area), but how does that explain the restorative force? If I move one
atom away from another, I'm moving the positively charged nucleus away
from this shared electron, so the electrostatic force between the
nucleus and the electron should only get smaller, not larger (as
hooke's law predicts).
The electrostatic/electromagnetic forces do get smaller with distance,
but if not seperated enough, they will "spring" back.
Take two magnets, hold them just far enough apart so you can feel
them pulling together, now move them close,
doesn't the force get stronger?
Now let them touch,
now bend the two so you open a gap in one side of the
touching sides.
Now let go..
Do you see any "spring" effect?
:)
I hope this is not "too simple" of an explanation.
If you wish a super complicated version,
ask a relativist.
:)
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| User: "Sam Wormley" |
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| Title: Re: Where does the spring force come from? |
08 Mar 2006 06:55:19 PM |
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Spaceman wrote:
Take two magnets, hold them just far enough apart so you can feel
them pulling together, now move them close,
doesn't the force get stronger?
Now let them touch,
now bend the two so you open a gap in one side of the
touching sides.
Now let go..
Do you see any "spring" effect?
:)
Spitshit, Spaceshit, Spaceman, or whatever you call the little
troll has quite the track record and is a registered crank at
crank dot net.
http://www.google.com/search?q=Spaceman+site%3Awww.crank.net
For a few laughs try the Spaceman [spaceshit] Emulator
http://www.hyperdeath.co.uk/spaceman/
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| User: "Sam Wormley" |
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| Title: Re: Where does the spring force come from? |
08 Mar 2006 06:48:49 PM |
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Spaceman wrote:
Take two magnets, hold them just far enough apart so you can feel
them pulling together, now move them close,
doesn't the force get stronger?
Now let them touch,
now bend the two so you open a gap in one side of the
touching sides.
Now let go..
Do you see any "spring" effect?
:)
Spitshit, Spaceshit, Spaceman, or whatever you call the little
troll has quite the track record and is a registered crank at
crank dot net.
http://www.google.com/search?q=Spaceman+site%3Awww.crank.net
For a few laughs try the Spaceman [spaceshit] Emulator
http://www.hyperdeath.co.uk/spaceman/
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| User: "Spaceman" |
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| Title: Re: Where does the spring force come from? |
08 Mar 2006 07:00:54 PM |
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"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:RXKPf.808343$x96.732103@attbi_s72...
Spaceman wrote:
Take two magnets, hold them just far enough apart so you can feel
them pulling together, now move them close,
doesn't the force get stronger?
Now let them touch,
now bend the two so you open a gap in one side of the
touching sides.
Now let go..
Do you see any "spring" effect?
:)
Spitshit, Spaceshit, Spaceman, or whatever you call the little
troll has quite the track record and is a registered crank at
crank dot net.
http://www.google.com/search?q=Spaceman+site%3Awww.crank.net
For a few laughs try the Spaceman [spaceshit] Emulator
http://www.hyperdeath.co.uk/spaceman/
Attack the poster, when you can attack the post itself.
Don't worry about Sam and his problem with spelling and such..
He is just showing you my post is fine.
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| User: "srp" |
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| Title: Re: Where does the spring force come from? |
08 Mar 2006 06:00:42 PM |
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a écrit :
We know that atoms are held together by atomic bonds and when one atom
is moved away from the one it's bonded to, there is a restorative force
that 'pulls' it back. But how can we explain the nature of this force
in terms of the electrostatic/electromagnetic forces between charged
atomic particles (proton & electron)? In a covalent bond an electron is
shared between two atoms
A little correction here. In a covalent bond, _two_ electrons are
shared between the two atoms.
(i.e. its wavefunction is spread over a wider
area), but how does that explain the restorative force? If I move one
atom away from another, I'm moving the positively charged nucleus away
from this shared electron, so the electrostatic force between the
nucleus and the electron should only get smaller, not larger (as
hooke's law predicts).
Brian
André Michaud
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| User: "SCW" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 05:44:29 AM |
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wrote:
We know that atoms are held together by atomic bonds and when one atom
is moved away from the one it's bonded to, there is a restorative force
that 'pulls' it back. But how can we explain the nature of this force
in terms of the electrostatic/electromagnetic forces between charged
atomic particles (proton & electron)? In a covalent bond an electron is
shared between two atoms (i.e. its wavefunction is spread over a wider
area), but how does that explain the restorative force? If I move one
atom away from another, I'm moving the positively charged nucleus away
from this shared electron, so the electrostatic force between the
nucleus and the electron should only get smaller, not larger (as
hooke's law predicts).
Brian
I'm not sure Hooke's law does predict this - it is an approximation of
elasticity and more commonly these day, elastic limit. Have a look at
the graph on the link below, and at point 2 (Yield Strength) - this is
elastic limit.
http://en.wikipedia.org/wiki/Hooke%27s_law
It's not a particularly good article, but the chart is more or less
correct.
Once past the yield point, the region becomes plastic not elastic, i.e.
it deforms and will not return to the pre-stretch shape. So to follow
the analogy in your question, you will reach a yield point after which,
there will not be enough attraction due to the electrostatic force to
overcome the inertia in the particle.
..
SCW
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| User: "" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 10:02:11 AM |
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My question though is why there is an attractive force in the first
place, which (at least for some distance) does increase when the atoms
are separated from each other. Since the atoms are separated farther
apart, the electrostatic force between them should be less, not
greater, if anything.
Brian
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| User: "Spaceman" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 10:11:46 AM |
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<vze2vt56@verizon.net> wrote in message
news:1141920131.258859.238260@u72g2000cwu.googlegroups.com...
My question though is why there is an attractive force in the first
place, which (at least for some distance) does increase when the atoms
are separated from each other. Since the atoms are separated farther
apart, the electrostatic force between them should be less, not
greater, if anything.
Where are you reading that the electrostatic force is greater
at a distance?
It is simply not true.
If I told you attractive forces were created from differentials
in pressure and no limits to the smallest "piece" of matter.
Would you think about it?
If I told you an electron and other "gatherings of particles"
can expand to over 1 meter and further simply by loss of surrounding
pressure of the same type parts?
Would you think about it?
If I told you that when the electron and other such gatherings do
such you can no longer see them since they are too small and
too spread apart but they still have a pressure that never reaches
absolute 0.
Would you think about it?
:)
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| User: "SCW" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 10:14:57 AM |
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wrote:
My question though is why there is an attractive force in the first
place, which (at least for some distance) does increase when the atoms
The answer to this is thermodynamics - there is less overall potential
difference when they are in combination than when they are seperate
entites.
[...] are separated from each other. Since the atoms are separated farther
apart, the electrostatic force between them should be less, not
greater, if anything.
Where do you get the idea that it is stronger at a distance?
Brian
SCW
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| User: "" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 11:17:19 AM |
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Take a metal spring. Stretch it some (small) distance x. Hooke's law
says there will be a force pulling the string back together, F=-kx.
Where does this force come from? If it's electrostatic microscopically
(i.e. electrostatic attraction between atoms), then shouldn't this
attraction decrease, and not increase, when you pull the atoms in the
spring apart?
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| User: "Spaceman" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 11:33:50 AM |
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<vze2vt56@verizon.net> wrote in message
news:1141924639.399410.172420@p10g2000cwp.googlegroups.com...
Take a metal spring. Stretch it some (small) distance x. Hooke's law
says there will be a force pulling the string back together, F=-kx.
Where does this force come from? If it's electrostatic microscopically
(i.e. electrostatic attraction between atoms), then shouldn't this
attraction decrease, and not increase, when you pull the atoms in the
spring apart?
Each one still does decrease.. but
You are pulling many smaller springs apart,
each single "spring" will still decrease in attraction force as it moves
away from the other,
but each single spring will also add to the total force pulling back
together.
After a while this "lesser attraction" will allow a break somwhere if pulled
far enough apart.
:)
Again,
take magnets and place them just far enough on a table that they
will almost attract but don't.
Now try the same distance with 2 magnets on each placement.
The force will increase simply because of the increase in magnets
and they will not stay apart.
The same is true with electrostatic forces also.
The more "single" forces the further they can still attract.
and the more of them there are will create more force
trying to pull it all back together again.
The force still decreases from a 1 to 1 point of view,
but when you have many to 1 you will see the higher ratio
of force until breakage of the many on 1 occurs.
:)
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| User: "PD" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 01:41:03 PM |
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Spaceman wrote:
<vze2vt56@verizon.net> wrote in message
news:1141924639.399410.172420@p10g2000cwp.googlegroups.com...
Take a metal spring. Stretch it some (small) distance x. Hooke's law
says there will be a force pulling the string back together, F=-kx.
Where does this force come from? If it's electrostatic microscopically
(i.e. electrostatic attraction between atoms), then shouldn't this
attraction decrease, and not increase, when you pull the atoms in the
spring apart?
Each one still does decrease.. but
You are pulling many smaller springs apart,
each single "spring" will still decrease in attraction force as it moves
away from the other,
but each single spring will also add to the total force pulling back
together.
After a while this "lesser attraction" will allow a break somwhere if pulled
far enough apart.
:)
Again,
take magnets and place them just far enough on a table that they
will almost attract but don't.
Now try the same distance with 2 magnets on each placement.
The force will increase simply because of the increase in magnets
and they will not stay apart.
The same is true with electrostatic forces also.
The more "single" forces the further they can still attract.
and the more of them there are will create more force
trying to pull it all back together again.
The force still decreases from a 1 to 1 point of view,
but when you have many to 1 you will see the higher ratio
of force until breakage of the many on 1 occurs.
:)
This shows you how far blind guessing will get you.
PD
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| User: "Spaceman" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 01:52:23 PM |
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"PD" <TheDraperFamily@gmail.com> wrote in message
news:1141933262.968132.67010@i39g2000cwa.googlegroups.com...
Spaceman wrote:
<vze2vt56@verizon.net> wrote in message
news:1141924639.399410.172420@p10g2000cwp.googlegroups.com...
Take a metal spring. Stretch it some (small) distance x. Hooke's law
says there will be a force pulling the string back together, F=-kx.
Where does this force come from? If it's electrostatic microscopically
(i.e. electrostatic attraction between atoms), then shouldn't this
attraction decrease, and not increase, when you pull the atoms in the
spring apart?
Each one still does decrease.. but
You are pulling many smaller springs apart,
each single "spring" will still decrease in attraction force as it moves
away from the other,
but each single spring will also add to the total force pulling back
together.
After a while this "lesser attraction" will allow a break somwhere if
pulled
far enough apart.
:)
Again,
take magnets and place them just far enough on a table that they
will almost attract but don't.
Now try the same distance with 2 magnets on each placement.
The force will increase simply because of the increase in magnets
and they will not stay apart.
The same is true with electrostatic forces also.
The more "single" forces the further they can still attract.
and the more of them there are will create more force
trying to pull it all back together again.
The force still decreases from a 1 to 1 point of view,
but when you have many to 1 you will see the higher ratio
of force until breakage of the many on 1 occurs.
:)
This shows you how far blind guessing will get you.
And where is the fault stated in the above PD?
What the heck is your problem with the statements I made?
What the heck is your problem at all?
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| User: "PD" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 02:53:28 PM |
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Spaceman wrote:
"PD" <TheDraperFamily@gmail.com> wrote in message
news:1141933262.968132.67010@i39g2000cwa.googlegroups.com...
Spaceman wrote:
<vze2vt56@verizon.net> wrote in message
news:1141924639.399410.172420@p10g2000cwp.googlegroups.com...
Take a metal spring. Stretch it some (small) distance x. Hooke's law
says there will be a force pulling the string back together, F=-kx.
Where does this force come from? If it's electrostatic microscopically
(i.e. electrostatic attraction between atoms), then shouldn't this
attraction decrease, and not increase, when you pull the atoms in the
spring apart?
Each one still does decrease.. but
You are pulling many smaller springs apart,
each single "spring" will still decrease in attraction force as it moves
away from the other,
but each single spring will also add to the total force pulling back
together.
After a while this "lesser attraction" will allow a break somwhere if
pulled
far enough apart.
:)
Again,
take magnets and place them just far enough on a table that they
will almost attract but don't.
Now try the same distance with 2 magnets on each placement.
The force will increase simply because of the increase in magnets
and they will not stay apart.
The same is true with electrostatic forces also.
The more "single" forces the further they can still attract.
and the more of them there are will create more force
trying to pull it all back together again.
The force still decreases from a 1 to 1 point of view,
but when you have many to 1 you will see the higher ratio
of force until breakage of the many on 1 occurs.
:)
This shows you how far blind guessing will get you.
And where is the fault stated in the above PD?
What the heck is your problem with the statements I made?
What the heck is your problem at all?
Oh, I know it would be fun for you to spout off and have no one
challenge what you say. It's just that when you spout gobbledygook,
there's a better than even chance that someone will ruin your fun.
PD
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| User: "srp" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 11:39:16 AM |
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a écrit :
Take a metal spring. Stretch it some (small) distance x. Hooke's law
says there will be a force pulling the string back together, F=-kx.
Where does this force come from? If it's electrostatic microscopically
(i.e. electrostatic attraction between atoms), then shouldn't this
attraction decrease, and not increase, when you pull the atoms in the
spring apart?
The atoms in your metal spring are held together mostly by
electrostatic force. As you stretch the spring, the force that you
have to exert increases as you stretch it simply because it is
insufficient to overcome this force, which obeys Hooke's law.
Similarly to the photoelectric effect, you need some threshold of
force to overcome the electrostatic bound, after which, the
electrostatic interaction between the separating atoms at the
breaking edges will start decreasing as electrostatic theory
warrants.
André Michaud
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| User: "PD" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 02:50:21 PM |
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wrote:
Take a metal spring. Stretch it some (small) distance x. Hooke's law
says there will be a force pulling the string back together, F=-kx.
Where does this force come from? If it's electrostatic microscopically
(i.e. electrostatic attraction between atoms), then shouldn't this
attraction decrease, and not increase, when you pull the atoms in the
spring apart?
First ask yourself the question what holds solids together at all.
Hint: General chemistry book, bonding chapter.
PD
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| User: "SCW" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 01:46:24 PM |
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wrote:
Take a metal spring. Stretch it some (small) distance x. Hooke's law
says there will be a force pulling the string back together, F=-kx.
Where does this force come from? If it's electrostatic microscopically
(i.e. electrostatic attraction between atoms), then shouldn't this
attraction decrease, and not increase, when you pull the atoms in the
spring apart?
Yes, this is slightly confusing, but it concerns the point of plastic
deformation.
In the case of the metal spring, the yield point is quite some time
after the stretch has begun, so the elastic region is easily
observable. Once the spring has passed the yield point, it will deform
plastically. It may still recoil, which is analogous to the
electrostatic attraction in the particle.
In the case of your particle, it reaches the yield point, and so enters
the plastic region, almost immediately - as soon as the particle starts
to move. This seems confusing because there is still a electrostatic
attraction, which could cause the particle to recombine and form a new
"spring"
..
SCW
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| User: "SCW" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 10:15:02 AM |
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wrote:
My question though is why there is an attractive force in the first
place, which (at least for some distance) does increase when the atoms
The answer to this is thermodynamics - there is less overall potential
difference when they are in combination than when they are seperate
entites.
[...] are separated from each other. Since the atoms are separated farther
apart, the electrostatic force between them should be less, not
greater, if anything.
Where do you get the idea that it is stronger at a distance?
Brian
SCW
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| User: "Sam Wormley" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 01:57:01 PM |
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wrote:
My question though is why there is an attractive force in the first
place, which (at least for some distance) does increase when the atoms
are separated from each other. Since the atoms are separated farther
apart, the electrostatic force between them should be less, not
greater, if anything.
Brian
I don't think you can visualize it that simply--springs are typically
made of metal, generally a crystallite structure and the forces
involved are complex and equally so for compression and tensile
stresses. I would suggest googling on some key words in the
previous sentence.
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| User: "PD" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 01:34:57 PM |
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wrote:
My question though is why there is an attractive force in the first
place, which (at least for some distance) does increase when the atoms
are separated from each other. Since the atoms are separated farther
apart, the electrostatic force between them should be less, not
greater, if anything.
Brian
It's easy to oversimplify here. The best thing you can do is to pick up
a chemistry book and go the chapter on bonding.
There is a balance between three different things going on here.
1. Electrons don't only feel the repulsion from the neighboring atom's
electrons. They also feel the attraction of the neighboring atom's
protons in the nucleus. In fact, in a bond, the electron in a bond
orbits *both* atomic nuclei -- and so what attracts it to the second
atom's nucleus is the same thing that attracts it to its own atom's
nucleus.
2. You should look up the "Aufbau principle" which normally is talked
about only in the context of a single atom's electron configuration.
But bonds one way for atoms to satisfy an "octet rule" -- the atom is
actually more stable if the orbitals in a shell are filled, and sharing
electrons is a good way to do that. It's actually more complicated than
that, and you can look in the same chemistry book about "hybrid
orbitals".
3. Too much sharing, however, and then quantum mechanics kicks in --
namely, fermion behavior and the Pauli exclusion principle. Too much
overlap of identical electron wavefunctions results in wavefunction
cancellation.
The result is that the potential energy curve is not the naive 1/r
repulsive potential you might think. Instead, it has a dip in it for
some finite radius. This radius happens to be half the bond length in a
diatomic elemental molecule.
PD
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| User: "Randy Poe" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 11:47:59 AM |
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wrote:
My question though is why there is an attractive force in the first
place, which (at least for some distance) does increase when the atoms
are separated from each other. Since the atoms are separated farther
apart, the electrostatic force between them should be less, not
greater, if anything.
The answer has to lie in quantum mechanics. That said, I
don't know all the details of the answer. But here's
a partial answer:
For any given bond between two atoms/molecules, there
is a preferred distance. This is the distance corresponding
to the lowest energy. To increase or decrease that distance
takes an input of energy, and thus the application of work.
There is a relationship between energy gradients and
force -- the spring "force" you feel is really the gradient of
the quantum mechanical potential. Gradients in potential give
rise to forces as systems attempt to return to minimum energy.
Now what I don't know is what sets that preferred length
and causes shorter or longer lengths to be higher
energy.
- Randy
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| User: "" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 01:08:34 PM |
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Ok, but how exactly do gradients in potential give rise to forces? In
classical physics it's more like the reverse: forces give rise to
gradients of potential (e.g. the electric field).
More importantly, how does this explain that the restoring ('spring')
force actually increases the more you separate the atoms, and does not
decrease.
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| User: "Randy Poe" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 01:58:53 PM |
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wrote:
Ok, but how exactly do gradients in potential give rise to forces? In
classical physics it's more like the reverse: forces give rise to
gradients of potential (e.g. the electric field).
I said that badly. As PD explained, they're equivalent. The electric
potential and the electric field are two different descriptions of the
same thing.
Ultimately in some way it has to be the Coulomb potential
at work, since that is the only interaction at work in
determining what are the stable electron states.
Here's a nice plot of the energy vs atomic distance:
http://www.science.uwaterloo.ca/~cchieh/cact/c120/bondel.html
More importantly, how does this explain that the restoring ('spring')
force actually increases the more you separate the atoms, and does not
decrease.
You'll get Hooke's Law behavior anytime your potential energy
function looks like a parabola near its steady state, which
is a decent approximation for a wide variety of curves.
The approximation doesn't hold far away from the minimum, but
neither does Hooke's Law.
- Randy
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| User: "PD" |
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| Title: Re: Where does the spring force come from? |
09 Mar 2006 01:39:47 PM |
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wrote:
Ok, but how exactly do gradients in potential give rise to forces? In
classical physics it's more like the reverse: forces give rise to
gradients of potential (e.g. the electric field).
No, one does not cause the other. They are *equivalent*.
More importantly, how does this explain that the restoring ('spring')
force actually increases the more you separate the atoms, and does not
decrease.
If the potential energy has a dip in the middle, then electrons will
settle into the dip (lowest energy state).
PD
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