WHAT CAUSES THE NORMAL FORCE?????
We all started from the basics of physics, that is the guru of the complete physics - LAWS OF MOTION. The one of the first things that we were taught were:Normal Force.
Did we ever worry to find out what it actually is and why it is?????
It has got electromagnetic reasons.........
Question was
I've been wondering, what causes the normal force to exist?
In class the teacher never actually explains it, he just says "It has
to be there because something has to counter gravity." While I
understand this is true, it never explains
why.
Whenever I ask anyone else they always respond in a similar way, saying
"It has to be there, because the object is not accelerating", and this
has become very frustrating.
So what is the cause of the normal force? From my reasoning, it has
to be one of the four fundamental forces. (Gravity, electromagnetism,
the weak force, or the strong force). It would seam to me that
electromagnetism would make to most sense (electrons in the outer shells
of atoms repelling each other),
However, just as I thought this had to be right, I read a thing
online about "certain fundamental particles repelling each other when
their wave functions overlap". I haven't studied quantum mechanics yet
so I'm not really sure what to make of that.
Answers came:
1.
The normal force is not really due to
any
of the four force of nature. The forces of nature are not all the
forces in the macroscopic sense, they are just the fundamental bosonic
particles in a modern quantum field theory description.
The normal force is due to the Pauli exclusion principle almost
exclusively. This is because electrons have the property that two
electrons cannot be in the same quantum state. Two electrons can't be at
exactly the same point.
But you might be thinking, "two point particles in three dimensions
can't ever be at the same point, it's infinitely improbable!" In quantum
mechanics, the particles are spread out in a wavefunction, and the
condition that they can't be at the same point means that wherever their
spread-out-ness overlaps, the wavefunction is zero. The wavefunction is
in 6 dimensions for 2 particles, so it is hard to visualize, but the
zeros appear on the diagonal part, where the two positions for the
particle coincide.
When you bring two objects to touch, the electron wavefunctions are
squeezed together, and the average scale of variation increases
slightly, because of the exclusion. The rate of change of the
wavefunction is the momentum of the electron, and as you push them
closer, it costs energy. This is the source of the normal force. It
would not exist if electrons were elementary bosons.
2.
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Assuming that by "normal force" you mean the one that acts against
the force holding the object to the surface: it's electromagnetic. As a
simple example, consider two interacting atoms. Basically, the force
between these atoms arises from three sources:
- The repulsion of their nuclei
- The repulsion of the electron clouds
- The attraction of each atom's nucleus to the other atom's electrons
If you graph the total potential energy of these contributions as a
function of the atoms' separation, you get something that looks roughly
like this:
Knowing that force is the negative gradient of the potential energy,
you can tell that the atoms experience a repulsive force when they are
close together and an attractive force when they are further apart. The
repulsive force gets larger the closer together the atoms are,
essentially without limit, so no matter what force is pushing the atoms
together, the system will reach some equilibrium point where the forces
are balanced (except under certain extreme conditions that never occur
on Earth). This illustrates how atoms are able to resist the forces
pushing them together.
Obviously, the real story is much more complicated because real
objects are made of molecules, and there are many different kinds of
interactions going on.
This isnt me: this is scripted from:
http://physics.stackexchange.com/questions/15055/what-is-the-cause-of-the-normal-force
After the question occurred to me i went googling and found this i think this is just the answer to the question!!!!!
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