Force
I am fairly certain the word force, and a definition for it, was in our language quite some time prior to Newton. However, he was the person that defined force in a scientific manner...
DEFINITION IV
"An impressed force is an action exerted upon a body, in order to change its state, either of rest, or of uniform motion in a a right line.
This force consists in the action only, and remains no longer in the body when the action is over, For a body maintains every new state it acquires, by its inertia only. But impressed forces are of different origins, as from percussion, from pressure, from centripetal force." The Mathematical Principles of Natural Philosophy, Newton.
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Newton's concept of force having "different origins" seems like an obvious conclusion by just looking at Nature then, and even now. Wind and water forces, for example. What isn't quite so obvious, is that people named forces by these origins. There is the force of the wind. The force of the water. Both of theses forces of wind and water do the same thing. They exert pressure. Pressure, which is the action of the force. Applying or bringing pressure to bear has common synonym names as push, shove, impel, impulse, thrust, ram, and etc. All this still seems straight forward... but as time passed this separation of a force origin name, and the action of a force started getting mixed up and confusing. The concept of the origin and action was not not given much thought in depth, or taught in schools. There was, and is another word that people use often along with force origin actions... and it is pull. The word pull has synonyms as jerk, tug, tow, yank, draw, and etc. We use this word as towing a trailer, yanking my hair out, tugging at your shirt-sleeve, and the pull of gravitation. The word pull is also listed as an antonym, or opposite of the word push. Okay, so what? I haven't told you anything you didn't already know; right? Well do you know__ when you pull anything; you are only exerting, or bringing pressure to bear__ in other words pushing? Technically when you are pulling, you are only pushing with leverage originating from in front of the entity being pushed, or having pressure applied! Yes it is true! Read my page in this section entitled Pull and Attraction for more detail. What this means is all forces pushing, and all forces pulling are actually force actions of exerting pressure. By eliminating Pull, and having only Pressure actions for forces it accomplishes some initial consolidation, and simplification of nature.
Now lets move on to the force of a vacuum. This word also has synonym words as suction, draw, inhale, and etc. Moving along a bit faster... The word vacuum is only a word to describe a low pressure area, or region, as compared to it surroundings. Any, and all areas of low pressure, i.e. vacuum, are created by using pressure to evacuate said same area! A vacuum pump is actually a pressure device. Simply put, a vacuum pump divides, or scoops a gulp of matter in Space and puts it somewhere else. They can be very efficient, but the vacuum created is not a true absolute void. There is always something remaining. Whenever there is a low pressure area, conversely there is a surrounding area of higher pressure. This is called a differential of pressure, in science and mathematics. All scenarios involving a vacuum can be be explained as a low pressure, and can be calculated as a differential of pressure. Furthermore all conditions of something being pulled, are calculated using pressure formulae. We, now have just made the category of forces of pressure larger encompassing all vacuums.
From Newton's writings... "percussion": percussion is not a special force action, it is either mechanical sound waves, or material vibrations, and they cause motion by Pressure. When Newton wrote of a force "From pressure"; he actually mixed the actions of forces with some of the origins of forces. Pressure is the action of motion, not the originating force, and more correctly it should be written as mechanical pressure, water pressure, wind pressure or etc... And lastly, "centripetal force". There is no such thing as centripetal force. Centripetal force would be the force origin, not the cause. I call this phenomena Centripetal Effect.
If a Hula Hoop is set revolving about a small diameter rod in deep Space (with minimal gravitation) it will go round and round as if in orbit. At the point of contact of rod and hoop, the rod is exerting pressure on the hoop, and the hoop is returning the pressure. This pressure is continuously changing the direction of the force as the hoop moves continually around. The culmination of all instant infinite straight lines of pressure of the complete 360° mutual contact of rod and hoop is: the incorrectly named centripetal force, and which I call centripetal effect. There is not one force, but an infinite number of straight line forces towards the axis of the rod. The hoop is also exhibiting its forward action around the rod due to the centrifugal effect, which is only actions of many forces always trying to go in a straight line forward, but cannot, due to being forced in a curve, (Law I, Newton).
[Using a bit more scientific strictness... when we say there is a straight line force acting in some direction, it is actually a culmination of many forces that are acting such that they focus as one, in one direction at any moment in time. If we say this a force is in a new direction, it is basically a shift of the focus of the forces.]
A kind of downside from Newton's work above is__ whenever we do not know the direct cause of the action of motion__ somebody will always come along and give the origin of the force a name__ electrostatic, magnetic, nuclear, atomic, heat, energy, electric, intermolecular, cosmic, frictional, drag, centrifugal, centripetal, electromagnetic, gravitational, weak, and strong forces to name a few. None of these forces tells you how, or the cause for a body going into motion, or changing state.
I need to also mention in the middle of all this discussion... Light. I cover light in Section III. Light is the an origin of force. But first, is for you to know; light is an electromagnetic phenomenon. Second, light means everything from low frequency 10 hertz (long wavelengths) to way up there about 10²² plus hertz (short wave lengths). The spectrum of light covers: power generation, audio, radio, television, radar, infrared, visible, ultra violet, x-rays, gamma rays, cosmic rays, and quantum phenomenon. Think about how small the size of a photon might be, and how many there are in the Universe. Imagine, how much light shines from just our sun (not just visible light, but heat, and etc.) and, the light (visible, as well as IR, Uv, and X-ray) from the stars, that fills the Universe... it is overwhelming. The quanta designated as a photon of light has the ability to do work, energy, in the form of pressure! Each and every active photon quanta in the Universe will bring impulse pressure to bear if it pressure impacts matter. This ability, of Light, to do work, i.e. energy, has the value of the frequency v, times Planck's constant h... (This pressure is due to the what I call directional mass) The enormity of the phenomenon of light in this Universe is staggering. And, it is all delivering potential force actions of pressure! Give some thought to it... even when it is dark... there is radio light waves, and light as heat radiation...
Particle radiation, is when an individual particle or particles are emitted or kicked free. Some particles are emitted from matter elements changing or decaying into different elements, or different conditions of an element. Some particles are blasted, pressed, out of an elemental atoms. Some only last for an instant, while others travel great distances in the Universe. Science has discovered many particles by the use of machines, called particle accelerators. Splitting the atom, or atom smashing were common expressions for these machines. Basically a particle or particles is accelerated to extreme speeds and then impacted, again pressured, into other particles. Literally, collisions were created, and science looked for the flying pieces! Again, if a particle races along and smacks into another particle as an impact collision; that is pressure of impaction. And, are not the flying particles from the collision, results of actions of forces of pressure impactions? "Nuclear energy: In nuclear fission, the energy released comes from the splitting of the atomic nucleus, resulting in the emission of nuclear particles such as neutrons, alpha particles, and beta particles." "Nuclear Fission: The splitting of the atomic nucleus, as by neutron bombardment, i.e. pressures. In an atomic bomb, nuclear fission is carried out so as to release great amounts of energy manifested by thermal radiation, nuclear radiation, and blast." §"Radiation Pressure: A pressure exerted by electromagnetic radiation on a surface exposed to the radiation. It is proportional to the radiant energy density in the neighborhood of the exposed surface." from Ency. Dict. of Electronics & Nuclear Engineering; Sarbacher.
The bottom line__ it appears that most, and a good probability of all, force actions in this Universe__ are pressure.
I would guess that there are upwards of a hundred various named origin forces. These force names do not convey the actions of these forces, and or how these actions work. The truth of the situation: it is factual that most of the existing named forces probably cause acceleration of an entity by pressure. The remaining unknown force actions causing change of state, should remain unknown, unnamed, and and un-assumed. It is still unknown exactly how gravitation holds the planets in orbit, and we do not know exactly how atoms hold things together. Something unknown it just that__ unknown; and the results of these actions can be described by words such as acceleration, motion, change of state, length, speed, velocity, and such, without assigning an assumed cause without knowing! It is also my strong suspicion, and logical analysis that the force causes of attraction are incorrect. Thus I suggest the word pull, and attraction, for science, should maybe have a definition accompanying the words, from the user, to express their meanings, as Newton did... thus minimizing misconceptions? (Again, for more information on attraction and pull, refer to my page titled Pull and Attraction. Two topics hence in this section) Furthermore for my use, I am going to continue separation of Force Origins from Force Actions!
Presently science thinks there are four basic fundamental force interactions. These are Gravitation, Electromagnetic, Weak and Strong forces. Gravitation is the force origin name for the actions of all bodies of matter having at rest mass, coming together. (excluding bodies coming together from the other three interactions herein.) Electromagnetic "is responsible for the forces that control atomic structure, chemical reactions, and all electromagnetic phenomena." The Weak force "is responsible for the beta decay of particles and nuclei." The Strong force "is responsible for the force between nucleons that gives the atomic nucleus it great stability." Science knows quite a bit about these force interactions... but in truth, they don't know how they work! To my knowledge, there has never been shown a pull to be accomplished without pressure being brought to bear, and intimate contact between the bodies interacting. Attraction is an "action at a distance" scenario and has very poor logic on how it would work, and has never been proved to be a viable action for any action of a force.
Again, bottom line__ This leaves us with only two actions of any an all, forces__ Pressure and Unknown!
§The definition of a Force should be something as: The first level identification origin leading to actions causing acceleration, and change of state of an entity.
The action causing changes of state (motion) is: the the changing of state of one entity intimately interfacing with a second entity... thus causing changes of state of the second entity. This action of a force, to date, has only been shown to be pressure collisions of entities fast or slow. I use the the words change of state, because there may be actions changing state, that may not just be a change of motions, but could be a change of condition. The intention of this detail is to allow for entities to have a change of state of field, or charge... (We do not really know exactly the physical composition of matter. I and we, mostly subscribe, and accept the logic that matter is a reality, and is an entity... but we cannot say exactly if a quark is a physical hard rock particle (unlikely), or is it an electromagnetic phenomena. This exact knowledge will most probably stay unknown.)
When an auto runs over a toad; it is squashed flat by pressure. When visible light impacts the rods in your eye; it is pressure. When a gas is heated; it is infrared light, impacting the molecules that become more active, and impact themselves more vigorously, and also colliding with the container walls increasing internal pressure. When an atomic particle is emitted, and or radiated, it is a high probability of pressure as the action. Light in an electron microscope will impact, pressure, an atomic particle such that it cannot be measured correctly. Brownian Movement is from pressure impactions on tiny particles in a liquid, due to the liquid's random molecular motion. Photons of light kick electrons loose, probably by pressure. The expansion and contraction of a metal bar is due to changes of internal pressure. Finally we have the sunshine from our star, the sun, basically keeping us alive, again from light pressure of photon quanta. By the typical experimental observed phenomena of this paragraph, and other logic throughout these writings, I again infer, and make the proposition: that the force cause action for any change of state is Pressure...
Yes, there are scenarios that I have no explanation, but neither does anyone else have any reasonable explanation. So I am going with the higher probability, and showing where other options are most likely bogus. This may be a situation of ten million swans doesn't prove there isn't, wasn't, or won't be one black swan... but it may be significant enough, not be lead into dead end theories, and might be incentive enough to investigate really how bodies of matter are pressed together by gravitational phenomenon.
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LAW I
"Every body continues in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it.
For the Universe of reality, and being more exact... Law I should be more like; Every body continues in its respective condition of changing state, of continual curved acceleration, unless it is compelled by additional force actions of pressure.
The Universe has no bodies in a "state of rest." There is, in truth, no exact "uniform motion", and there is no exact "right (straight) line." The last line of "forces impressed" is correct, but probably not meant as strictly as I purport. "Impressed" is a word meaning pressure applied.
Newton's Law I seems simple enough. If a body is moving through Space with minimal friction, minimal gravitation, and in a straight line, it will continue for a long while, unless it is forced with pressure to do something else. This is not difficult to understand. However, Newton also wrote: a spinning toy top in this same Space will also keep going for a long time. This spinning top bothered me. I never really thought about this until today; (9-19-2009, if you're keeping score). (There is probably an explanation to this spinning scenario, in one of my books; and I surmise I knew this at one time.) It had me going for awhile, but I thought it over, and here is what I came up with__
A toy top or any other body of matter however irregular, if set spinning, will tend to spin about its "center of gravity", or its middle balance point, so to speak. This way it has an equal amount of matter on one side moving 180° out of phase with equal matter on the opposite other side, continually for 360°. This balance is maintained in the plane of the rotation. This phenomena is demonstrated by a bola thrown by an Argentine cowboy, a boomerang thrown by an Australian Aborigine, or a youngster throwing a Frisbee. (Note: It might be possible to throw a spinning Frisbee a distance of light years in Space.) Anyhow, there would be force actions of matter trying to go straight, throughout the spinning body. These are the conditions of centrifugal effect, which results in an exact naturally balance. This would give us null force actions that are equal and opposite at equal radii about a single axis; for a total resultant of zero null, in all directions across the plane of the spin. And since there is very little friction or gravitation in deep free Space, the body would spin for a long while. At any instant all the particles of matter of any spinning body are yet just demonstrating Newton's first law; of particles trying to go in right (straight) lines.
There is also a centripetal effect for the spinning toy top, holding the spinning solid bodies of atoms, and or molecules together as a solid. I read where the particles of atoms are held together due to an "exchange of particles". However, this really doesn't tell me how they do it. It is like the Hatfields and the McCoys feuding with each other, and exchanging lead bullets. Exchange alone, won't bring the bodies together. In fact, if the particles are emitted under pressure, it might drive the bodies apart... Newton's Law III.
But anyway__ if the spinning body was as a wheel made of chain spokes... it can be demonstrated how centripetal effect works. It is like the hula hoop. In the center, all the chains are fastened to an axle. When the chains are spinning they all stand out more or less straight from the middle. The first link of each spoke is hooked around and pushing the inside near surface of the second link; the second link is hooked around and pushing the inside near surface of the third link, the third link is hooked around and pushing the inside near surface of the fourth link... and etc., etc., etc. There is constant inward pushing but the direction is constantly changing. This center pushing (pressure) is the centripetal effect.
After I wrote the above three paragraphs, I went to my collection of physics books to see what they had to offer. Some books didn't have anything, and the others seem to jump into "rotational momentum, conservation of momentum, moment of force... i.e. torque which is force" and etc. Which may be okay; but... these additional items would need explanation...? I'll just go with what I have above.
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[It is my contention, and belief__ that the cause, or explanation for any and all motion or change of state, is a result of pressure. If you like simple__ it doesn't get any better than this!]
[Pressure is the action of all forces, while named forces are the first level origins of the pressure.]
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The reason I qualified origin above as a first level... is to not get caught in absurdities such as the heart pumps blood to the muscles that move my arm that squeeze my fingers that exert pressure... etc., etc... Sort of like a wart on a frog on a log in a pond in a field near the town... In a more scientific vein, I want to keep the observed frame of reference focused close to the action of force, the pressure. What is the moving finger doing at intimate contact with the book that is sliding across the table? Not: what is the body doing, the arm doing, the hand doing, and etc? But, if taken to very extreme thinking... everything in the Universe is interconnected__ never without curved motion, acceleration, and pressure... it is only a discussion of how much for one something, relative to any or all other things!
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LAW II
"The change of motion is proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed.
Note the word impressed twice in Law II... to impress is to apply pressure...
Newton's Law II... In order to cover the subject of force, I need to go over all three of Newton's Law's. Now, Law II... This Law is "quoted" here and below, with his explanation, for you as he wrote it... But, the science of physics has progressed, and we can be a bit more scientific when referring to the mechanics of bodies coming together... So I vary a bit from the physics of Newton. Remember there is really no exact "right line."
I have separated the named forces into Named origins for forces. I also now have the actions of forces separated. I further rendered actions of forces, as the singular phenomena Pressure, as the action of all named force origins... Thus it is obvious that I must change things a bit...
I still retain the concept of acceleration. I use the concept of rest or at rest mass for a body since it is the best way we know, to have a common way of measuring all the various types of matter. As mentioned I now have the action of all forces as pressure. This may be my downfall, but it seems to have good sensible strong reasoning for the choice. One strong reason is that a single force action for all force origins makes pressure a simple single common denominator. Lastly and very importantly: I qualify pressure for the following formula as the change of state of bodies (motion)__ as Differential Pressure.
Δ P = ma
Stated as a word formula it is:
[If there is a change of state of a body of matter, of a measured mass, and it has been accelerated into motion, it was an action of differential of pressure. From the instant the pressure is applied there is a differential... The differential is the difference from the point of pressure contact to where it is headed. This differential of pressure can be from within the body as recoil or spring back from a compression. When the differential of pressure ends, the acceleration ends. The acceleration is directly proportional to the differential pressure, and inversely proportional to the mass, as always.
The reasoning for specifying a differential is twofold: First, whenever there is an acceleration there is a differential of pressure. Whenever the acceleration ceases, the differential of pressure is also gone. However, it is possible to have pressure without having acceleration. But, there is never acceleration without a differential of pressure. (Refer to my page on Pressure.)
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LAW - III
"To every action there is always opposed and equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.
In my reality section under title: Pressure, I go over topics that relate to Law III
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Why do I have Force in Section II, the fantasy section? Well, I look at the origin or name for a force__ as just that. No-one has ever seen, or sensed, the origin of a force. We only have felt pressure, and observed effects of other things we suspect as a force that has acted, but are not all in agreement of the action of the force. The "how". The things that are the origins most likely are all real thing in our Universe, but fall into the real category of matter in motion, and if they collide with other entities will cause a change of state. (Hitting a real brick wall does not usually indicate any motion, but, for a short instant there was real measurable pressure, and some atoms and molecules did move for a momentary change of state.) Water does not know it is the water force origin of erosion of a creek bank. It doesn't even care! It is just "Doing what comes naturally!" There is real water, there is real motion, there is real pressure, there is a real earthen creek bank, so the result is moving real mud. Nary a soul has ever spied a mud force!
I might just mention here, I am not throwing topics like energy, mass, and force... out the window forever more! They are here to stay and use, hopefully correctly. They are wonderful! I am a philosopher when I write thusly, and I am only sorting out, and correcting physics; hopefully to move science and mankind along a new more productive path...
We have lots of force origins. Wind, water, heat, light, physical, sound and etc... So we would normally say: wind force, water force, heat force..., but why? I have shown good cause that all know force actions are pressure. Thus we can skip the word force and relate forces as wind pressure, heat pressure, water pressure, electromagnetic pressure and etc. The word force is not really needed for reality. Pressure instead, is the reality.
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Page Relevant Quotes
DEFINITION IV
"An impressed force is an action exerted upon a body, in order to change its state, either of rest, or of uniform motion in a a right line.
This force consists in the action only, and remains no longer in the body when the action is over, For a body maintains every new state it acquires, by its inertia only. But impressed forces are of different origins, a from percussion, from pressure, from centripetal force." The Mathematical Principles of Natural Philosophy, Newton.
LAW I
"Every body continues in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it.
Projectiles continue in their motions, so far as they are not retarded by the resistance of the air, or impelled downwards by the force of gravity. A top, whose parts by their cohesion are continually drawn aside from rectilinear motions, does not cease its rotation, otherwise than as it is retarded by the air. The greater bodies of the planets and comets, meeting with less air resistance in freer spaces, preserve their motions both progressive and circular for a much longer time." The Mathematical Principles of Natural Philosophy, Newton.
LAW II
"The change of motion is proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed.
If any force generates a motion, a double force will generate double the motion, a triple force triple the motion, whether that force be impressed altogether and at once, or gradually and successively. And this motion (being always directed the same way with the generating force), if the body moved before, is added to or subtracted from the former motion, according as they directly conspire with or are directly contrary to each other; or obliquely joined, when they are oblique, so as to produce a new motion compounded from the determination of both." The Mathematical Principles of Natural Philosophy, Newton.
LAW III
"To every action there is always opposed and equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.
Whatever draws or presses another is as much drawn or pressed by that other. If you press a stone with your finger, the finger is also pressed by the stone. 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; for the distended rope, by the same endeavor to relax or unbend itself, will draw the horse as much towards the stone as it does the stone to the horse, and will obstruct the progress of the one as much as it advances the other. 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 changes made by these actions are equal, not in the velocities but in the motions of bodies; that to say, if the bodies are not hindered by any other impediments. For, because the motions are equally changed, the changes of the velocities made towards contrary parts are inversely proportional to the bodies. This law takes place also in attractions, as will be proved in the next Scholium." The Mathematical Principles of Natural Philosophy, Newton.
COROLLARY I
"A body, acted on by two forces simultaneously, will describe the diagonal of a parallelogram in the same time as it would describe the sides by those forces separately." The Mathematical Principles of Natural Philosophy, Newton."
"...Aristotle had believed that a force is necessary to maintain continuous motion." Quanta: J. Andrade e Silva, G. Lochak
"We all know that electromagnetic waves transport energy. Perhaps you also know that such waves can transport linear momentum. That is, it is possible to exert pressure (a radiation pressure) on an object by shining a light on it." Fundamentals of Physics: David Halliday, Robert Resnick, Jearl Walker.
"Lord Rayliegh pointed out that, in an ideal fluid, a ships propeller would not work, but on the other hand, a ship (once set in motion) would not need a propeller." Fundamentals of Physics: David Halliday, Robert Resnick, Jearl Walker.
"Heisenberg uncertainty principle; principle of indeterminism: The principle that it is not possible to know with unlimited accuracy both the position and momentum of a particle. An explanation of the uncertainty is that in order to locate a particle exactly, an observer must be able to bounce off it a photon of radiation; this act of location itself alters the position of the particle in an unpredictable way. To locate the position accurately, photons of short wavelength would have to be used. The high momenta of such photons would cause a large effect on the position. On the other hand, using photons of lower momenta would have less effect on the particle's position, but would be less accurate because of the long wavelength." A Concise Dictionary of Physics: Oxford
"...laws of motion... The story began with Galileo... Of all his discoveries, the greatest was that a body upon which no outside force is acting will continue in its state of motion; if it is at rest, it will remain at rest, but it will maintain any velocity that it originally has. This is the principal of inertia, the first of the great principles of physics of which the general statement was probably given by his contemporary Rene′ Descartes." Quanta: J. Andrade e Silva, G. Lochak
"Newton concluded that the acceleration given to a body by any particular force will be independent of the form, dimensions, and constitution of the body; it will depend entirely upon the amount of matter that the body contains__ in other words, its mass. The fundamental law of dynamics is:
F = mγ
where m is the mass of the moving body, F the force acting on it, and γ the acceleration produced. This law shows quite clearly that the only property of the body which is relevant to the study of motion is the mass." Quanta: J. Andrade e Silva, G. Lohak
"Under no conditions does there ever exist such a thing as 'centrifugal force'. No force pulls the object outward, nor does it move outward when let go." Particles in Nature; John H. Mauldin
"The apparent simplicity in the collision of billiard balls is quite illusory. As a matter of fact the two billiard balls never touch at all; what really happens is inconceivably complicated, but is more analogous to what happens when a comet penetrates the solar system and goes away again than to what common sense supposes to happen." The ABC of Relativity; Bertrand Russell
"All waves, whatever their nature, carry momentum as well as energy. This makes itself felt whenever they are reflected or absorbed, for in both cases there is a rate of change of momentum, and that means force. We can use this fact to measure the rate of transmission of momentum in radiation by defining the force per unit area, i.e. pressure, exerted on an absorbing surface, and we speak of radiation pressure. The radiation pressure exerted by sunlight is minute, but in huge, massive stars the radiation may be so intense that the pressure it exerts on the electrons and protons of which the star is composed is the major prop against gravitational collapse." Time, Space and Things; B. K. Ridley
"By the mid-20th century four fundamental forces in nature had been well established. these are in order of historic discovery, gravity, electromagnetism, the strong nuclear force, and the weak force... The reader may wonder about the other forces experienced every day. Why did only gravity make the list of fundamental ones? Our experience includes pushes and pulls we can make with our own muscles and with our engine-powered vehicles. These are legitimate forces in physics but are not fundamental. The four fundamental ones will be seen to apply to four very distinct realms of nature. As we learn more about the structure of matter we shall see that the electromagnetic force is the basic one at work when one object pushes or pulls another...
We have all experienced certain aspects of electromagnetic force directly. In regard to the electric part of it, we have noticed that a comb drawn through hair then attracts bits of paper, pulling them with some force." Particles in Nature; John H. Mauldin.
"Centrifugal Force
When we round a curve in a train or automobile, we experience the familiar sensation of a force pushing us towards the outside or the curve. Mud thrown from the moving wheel and the pull of a stone whirled on the end of a string are other manifestations of this force, which is known as centrifugal ('center fleeing') force. However, strictly speaking, it is no more than another name for inertia; when our car rounds a corner, we tend to keep going in a straight line and therefore feel as if we were being pushed to one side of the car. Centrifugal force is simply an expression of the reluctance of moving bodies to change their direction of motion." Fundamentals of Physical Science; Konrad Krauskopf, Arthur Beiser.
"...the centrifugal force is fictitious__ it does not exist." A Concise Dictionary of Physics, Oxford University Press Reference.
...So Einstein's law of gravitation contains nothing about force. It describes the behavior of objects in a gravitational field----the planets, for example----not in terms of attraction but simply in terms of the paths they follow."