F=μmg. How was μ calculated? Obviously experiments were

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In summary, the conversation discusses the calculation of the coefficient of friction (μ) and its empirical nature. The participants also mention the types of friction (static and kinetic), the challenges of predicting friction in different weather and road conditions, and the use of experiments to determine μ. They also mention examples from a physics textbook and question the validity of the free body diagrams and force analysis. The conversation concludes with a request for proof or evidence to support the force analysis.
  • #36


Anyway, let's say that "I am confused and there is no question".
However, some of my conclusions so far are:

The definition of Force is
mdu/dt= (mass)(the acceleration of the mass which happens visibly-macrocosmically)
so it's resultant force that sometimes happens.

mg can only be mdu/dt, there's no other proof that the force of gravity is that much, besides the acceleration of a mass at free fall.

Therefore, the definition of all forces besides the resultant, is unknown, and it is upon us to guess what they might be e.g. the mdu/dt that would had happened if the other non-resultant forces were not happening together. Or, that they might be momentums=(mass)(velocities) that strike the m (I call these green momentums).

So, one quess is "if the canted wall did not exist, the mdu/dt would be mg", so n is...?
 
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  • #37
Perhaps you should review these:

* http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/video-lectures/lecture-3"
* http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/video-lectures/lecture-6"
* http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/video-lectures/lecture-7"
* http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/video-lectures/lecture-8"
 
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  • #38


luckis11 said:
Anyway, let's say that "I am confused and there is no question".
However, some of my conclusions so far are:

The definition of Force is
mdu/dt= (mass)(the acceleration of the mass which happens visibly-macrocosmically)
so it's resultant force that sometimes happens.

mg can only be mdu/dt, there's no other proof that the force of gravity is that much, besides the acceleration of a mass at free fall.

Therefore, the definition of all forces besides the resultant, is unknown, and it is upon us to guess what they might be e.g. the mdu/dt that would had happened if the other non-resultant forces were not happening together. Or, that they might be momentums=(mass)(velocities) that strike the m (I call these green momentums).

So, one quess is "if the canted wall did not exist, the mdu/dt would be mg", so n is...?
If you ignore the air particles, then the normal force (or what you call n) should be zero (since there isn't any normal force, since we are ignoring internal forces).

If you don't ignore the air particles, then the air particles hit against the falling body (which causes the momentum of the air particles to transfer from themselves to the falling body) we call this "air drag" which eventually gets bigger (because you hit more particles as you speed up due to gravity going down) and eventually the transfers of momentum will stop you from accelerating since so many particles will strike you.

An atom is at rest on Earth's surface and Gravity is pulling down on it. However the atom does not go through the Earth because another atom is under it. The atom under it is one of the atoms of the ground. As the atom on top is pushed down by gravity, the outer electron shells of the top atom and the bottom atom begin to repeal each other, since same charged particles repeal each other.

The force of the "repeal" is the normal force. As the top atom is pushed closer to the bottom atom by gravity, the repellent force of their electron shells grows until it has the same magnitude and direction as the force of gravity. (The atom under the bottom atom does the same thing and so on until you get to the center of the earth.)

Here people deem them to be "still", but since energy is conserved, eventually the electrons outer shell force or pressure (which is called Electron degeneracy pressure) would weaken and then the electrons would collapse into the nucleus of the atom. Hence, electrons are accelerated toward the center of the atom. People tend to ignore this fact because it's hard to observe and usually so small that it is negligible.

However, this only occurs when a lot of joules (energy) is applied to the electrons. Since the force of gravity is relatively weak in this scenario, it would not happen in a very long time.

The same thing occurs with multiple atoms and compounds, the electron shell "fights back" sometimes forming a bonded outer shell (hence compounds) in structures.

Edit: I am ignoring all the atoms under that bottom atom for simplification

luckis11 said:
mg can only be mdu/dt, there's no other proof that the force of gravity is that much, besides the acceleration of a mass at free fall.
Everything is a guess. But what I think your doing is decomposing every structural logic until nothing else is left of it. Sounds like something a teenager would do. Luckis11, Do you know the difference between force and acceleration?

Wikipedia: In physics, a force is any influence that causes a free body to undergo a change in speed, a change in direction, or a change in shape.

The electrons shape is changing, they are being compressed at an extremely slow rate.

I hope this clears some confusion, and I hope I've guessed right.

Edit: I over simplified some facts in my explanation. I did so because I do not want to write a "thesis" which would be too long for most people to want to read.
 
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