Force
In classical physics, if a body was accelerated, it is said that it had a Force act upon it. (Again I am referring to a body classically and not the micro world particles.)
LAW III
"To every action there is always opposed an equal reaction: or, the mutual actions of two bodies upon each other are always equal, and directed to contrary parts."
The Mathematical Principles of Natural Philosophy, Newton.
(Law III is for classical physics, otherwise it would mean that two opposing exactly equal pure iron balls coming together, at exactly the same rate of motion, in a perfect vacuum, in a straight line__ with exactly the same number of atoms, in the exact same mirror image locations, moving in exact unison with the mirror actions of the opposite ball__ with no outside gravitational or electromagnetic interference __ in an empty universe with no curvature, they might have a chance of equal and opposite reactions?!)
It is true that when I press upon something it presses back, but if while I am pressing__ the body pressed upon__ is being compressed in motion away from the pressure, there is a differential of pressure, and the pressure being applied is more than the receding back pressure. At extremes there are not any two exactly equal bodies. But, when two bodies near to being equal come together directly in motion mutually, they each create a pressure upon the other that causes a compression in each that is a differential pressure within each body.
When any pressure is in action as above described as a differential pressure acting upon a body to cause motion it is a Force. Only when this pressure force is in action causing motion is it an acceleration. (This means motion of the body generally in whole or physical parts... not molecular or atomic motions.) In the extreme sense... any force of pressure is causing motion as long as it persists, but the acceleration may not be outwardly materially noticeable.
There is acceleration within a body as it compresses. There is acceleration also as the body expands from the compression. Classically speaking once the body is totally set into a new state of motion the acceleration has stopped, and it is said to have been accelerated. Accelerated, the past tense of accelerate!
When any body is pressed it has some amount of compression. When one side of any body is pressed into motion, the opposite side is not set into instant motion.
There is some distance through any body, and even Light has a travel time, so there will be a differential of pressure. This applies for any body being mechanically or gravitationally accelerated.
LAW III (Explanation)
"If a horse draws a stone tied to a rope, the horse (if I may say so) will be equally drawn back towards the stone;"
(To even have good meaning in classical physics this statement of a horse and stone needs to be re-evaluated to put it as a statement of pressures being applied to the fastened loop ends of the rope attaching the horse and stone, and eliminating the word drawn, which equates to a pull. RAD)
"If a body impinge upon another, and by its force change the motion of the other, that body also (because of the equality of the mutual pressure) will undergo an equal change, in its own motion, towards the contrary part."
The Mathematical Principles of Natural Philosophy, Newton.
I suggest:
If a body is set into motion that changes its state; it is being accelerated by a force, and therein exists a differential of pressure for the duration of the acceleration.
Again__ A Force of pressure is being applied__ A body is changing state__ It is in motion__ Acceleration is occurring__ There is a differential of pressure.
I say again: If the opposing action is exactly equal in magnitude... time, distance, pressure, and etc__ it can only be a null zero condition and no acceleration is happening, and no force is acting. RAD
If a balance of pressure exists between two bodies, a null occurs, and there is no noticeable external motion, there is no force acting and no acceleration. 4/19/2006 Note: There is the instant of null when two bodies collide__ both accelerating to zero as they compress, and then expanding acceleration in reverse to whatever rate they obtain based on the initial collision parameters. But, this is probably never a true null, due to the internal complexity of the bodies never coming to complete stop and then restarting. There will be a multitude of coming and going throughout each, at the atomic particulate level. (Refer back to my acceleration page for more on internal body acceleration...)
There can be pressure applied with no motion, for classical physics purposes. This is not a force since there is no acceleration. (Once any initial mutual internal acceleration comes to a null.) If I am pushing a brick wall with no noticeable motion, I am applying pressure but no force is in action. I have not accelerated the wall. (I realize that there can be work being done when I am pressing upon a wall, and energy is expended as heat, due to increased atomic agitation at the micro level... But, remember I am working with classical bodies as mentioned...)
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Pressure is not always a force. (Classically speaking)
This is due to the vector mathematical definition of Force:
F = ma
However, this vector formula might be changed as such: Differential Pressure (delta P) equals mass times acceleration... Since with no differential of pressure there is no acceleration, i.e. no motion.
ΔP = ma
Note: If adhering to strict Extreme Physics... It appears the matter/mass of Universe is in total curved motion. This means: Whenever there is Motion, there is Acceleration... Whenever there is Acceleration, there is Force... Whenever there is Force, there is Pressure... Whenever there is a Force of Pressure, it is a Differential Pressure. These items are all Universally inseparable, continuous, and total. Thus we can for the Extreme picture reduce the items to Pressure equals mass times motion for a vector mathematical formula:
P = mM
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I group the word force, in two definition types. Rigid, rigorous, strict, specific, or conservative when speaking or writing in terms of forces acting in the Science of Physics. And, loose, flexible, lenient, general, or liberal for forces that are not related directly to causing an acceleration of the body.
When we speak of an armed force, or brute force, or emotional force__ it is easy to relate to what I mean as a loose usage of the word force.
But, where it becomes confusing is with titled concepts such as Strong Force, Weak Force, Gravitational Force, Centrifugal Force, Centripetal Force, Attractive Force, Pulling Force, and the like__ which all are used in the Science of Physics!
These just mentioned forces are phenomena that are observed actions or effects that are not fully understood, are multiple action effects, or misrepresented actions. When analyzed they are descriptive of actions that contain multiple acting basic force actions.
(Note: Even a force, in the rigid sense, is actually not any one force, but collectively all the little forces intimately in action at the local frame of observed reference. Pushing a book with my finger is not any single pinpoint shaft of force. But, pushing a book is a singular basic type of forcing action. There are many, many atoms and particles, waves, or whatever in action at the micro level. But, the book moving in one direction can be described as a single straight line direction of force.)
All force is nothing more than a differential pressure, but I will continue to use force as a convenient word. It can describe different types of pressure sources. Mechanical, heat, magnetic, and etc., which are still pressure but seem to have variances of how the pressure is executed or derived.
I can line up 100 dominos such that when I push one over it pushes the next, and the next, in a series, as we did as children, until they all topple. This is not a Force of Dominos. There was a force that I exerted to start the sequence, but then it became a series of independent accelerations consisting of many forces.
There is really no centrifugal force. We might call it an action or effect. The centrifugal effect is nothing more than classical Newton's 1st Law in action. Spinning a ball on a string, water spun about in a bucket, going into the car door in a turn, can all be easily explained, and demonstrated as bodies of matter just attempting to go straight.
There actually is no such thing as a Centripetal Force.
Choke! Choke! Attractive Force! Noooooooooooo!
Repulsive Force? No... this is just pressure. It can fall into the rigid group.
Gravitation has its own chapter later. But, it is an effect or actions, not an overall magical force.
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(4/19/2006) I think I will rescind what I said above about "continuing to use the word Force", especially when referring to items of physics. I would like to try to explain my physics using the word Pressure in place of Force.
We can mechanically squeeze a container of gas vapor. This squeeze exerted pressure. The walls of the container press inward on the gas. Exerting pressure on the gas. The gas molecules have less room to move, resulting in increased collisions with each other, and the container walls__ exerting more pressure throughout. The temperature of the gas increases, which is an electromagnetic phenomena, light, in the ultra-violet frequency range that is being radiated. This heat is due to increased molecular agitation. If the pressure is taken to a high enough value, and depending upon the type of gas, we can create a uncontrolled rapid expansion of gas chemical reaction, called an explosion! If this is harnessed for our use, we put it to what we call Work. Such as a diesel engine. This diesel engine can then put pressure on gear teeth, they in-turn use pressure to turn wheels, which could coil up cable to lift items... and pressure can be traced all throughout this scenario... Work and related measurements abound in our physical world. The lever, an innovation we discovered, rates very high upon the scale of importance to mankind. (Please note: the wheel is truly a lever at any one instant!) The lever is solely and only an instrument of pressure.
But, back to three billion years ago. There was no work being performed. There was a whole lot of change going on, but not as intentional work for the benefit of mankind. The work being performed was creating and destroying heavenly bodies. Once Earth was created it was then mostly on a spiral of destruction we call entropy.
This changing of the Earth did form a habitable place for life. This could be called God's Work! But, I do not think God sits in a control room, and manages every speck of rust (oxidation), or every drop of rain. And, for physics, we don't measure God's work in dynes, ergs, kilowatts, and etc.
Way back prior to life... Earth did not have machines, and use leverage to move a rock, or re-route lava. But, if we were there 3 million years ago__ we could recognize the manifestation of pressure in use; it would be quite evident. So like force, I am going to drop the word Work. We can use the pressure of gravity to do work, but work, and force should not play a part in the actions of gravity. Gravitation can and does act without the words work and force.
