Talk:Centrifugal force/Archive 1

This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.

Untitled

Dear Author: Centrifugal force actually is a force. Your article contradicts itself by saying that this force is not a force yet admits that this "non-force" carries with it the force attributes of magnitude and direction. This definition and description of centrifugal force is without hope. It is not possible to modify it sufficiently to arrive at the truth. Such a modification would have to set aside each and every misstatement made herein regarding centrifugal force.

Would you like another example? The term "inertia force" is employed. No expert on "inertia" claims it is a "force". "Inertia" actually is nothing more real than our recognition that when no true acceleration/Action force is impressed upon an object, the object has no other choice to continue with its motion unchanged. This is the default state of motion of an object for which no cause exists. Certainly not an imaginary "inertia" cause. So to use the term "inertia force" is to use a term that is devoid of meaning.

Another? Centrifugal force is present within every rotating object regardless of whether the object is being considered from a non-rotating reference frame or a rotating reference frame. It does not exist exclusively within a rotating reference frame as claimed. All that is required for the centrifugal reaction force to exist is for the object to rotate or orbit about some central axis. This rotation or orbit is absolute and need only be compared to the same object when it is not rotating or orbiting about the axis.

Another? Centrifugal force never "acts" away from the center of rotation. It "reacts" in support for the only action force present, the inward-directed centripetal acceleration/Action force.

Another? Centripetal force is the action force responsible for causing the activity of inward-directed acceleration. The term "constrain" does not offer a good description for the action of acceleration. In a linear event would you say that the force from the tires "constrains" the vehicle to increase its speed down the road?

Another? Why quote Newton's 1st law in support of the existance of the centripetal acceleration/Action force but then follow with a statement in direct contradiction to Newton's 3rd law? When you say that "This force is the centripetal force, the only force necessary for a circular motion." are you not forgetting that for every action force there always exists an equal and opposite reaction force? Whirl an object in a circle using an attached rope. How can you think it possible for the rope to apply an inward-directed centripetal acceleration/Action force to the object without the object reactively applying an equal and opposite outward-directed centrifugal acceleration/Reaction force to the rope? Newton recognized long ago that contact forces are always mutual. In reality your rope cannot apply even the slightest force to the object without the presence of a centrifugal force from the object. So when you say the centripetal force is the only force necessary for a circular motion, your readers are burdened with yet another untrue statement. Here you can insert an ordinary tension scale between the rope and the object to verify the presence of both the centripetal acceleration/Action force and the centrifugal acceleration/Reaction force. Here the scale does not support your illogical statement that only one one force is necessary. Further, the scale does not support your illogical statement that "centrifugal force is not a force."

Another? In the absence of an inward-directed centripetal acceleration/Action force, the object doesn't have a "tendency" to travel in a straight line. "Tendency implies that the object has other choices. In fact, no other choice exists. Once the centripetal acceleration/Action force goes missing the object has no other choice but to ALWAYS revert to its default state of unaccelerated straight-line motion for which no cause exists. Of course once the centripetal action force goes missing, so goes the mutual centrifugal reaction force.

Another? I think you end by implying that Physics teachers who teach that centrifugal force is a reaction force that balances the centripetal action force, are somehow doing their students a disservice. If I have this right, let me end by saying that such teachers are much closer to teaching the truth about centrifugal force than most of what is written in this article.

Sincerely,

Ethan Skyler http://wwww.PhysicsNews1.com/article_11.html

You seem to have a misunderstanding what the label "centrifugal force" refers to. Let's take the rope and bucket problem.

You spin the rope+bucket around, and get up to speed. Now, here's a summary of the relevant forces on the rope and bucket:

inward tension on the rope from your arms.
inward force applied by the rope to the bucket, and its counterforce from the bucket applied to the rope.

None of these is centrifugal force. Centrifugal force is the appearance, from your viewpoint at the center, that there is some mighty force trying to pull the bucket outward. This "force" is not real, has no 3rd law counterforce, and is caused by inertia's straight line effects in a rotating reference frame.

Another example: put a hypothetical frictionless platform on the back of a flatbed semi, and stick some reasonably massive object on top of it, like a refrigerator. Carefully accelerate the truck and refrigerator up to speed. (we're going to ignore air resistance because it isn't relevant).

Now take the truck and put it on a circular path to the left. From the non-rotating frame of reference of a person standing on the ground, the refrigerator will follow a straight-line inertial path until it leaves the truck and gravity kicks in. No centrifugal "force" involved.

But from the frame of reference of the truck, something very strange is going on. From the truck's standpoint, the refrigerator has accelerated right off the frictionless platform, with no apparent cause. The label given to the mysterious cause of this acceleration is "centrifugal force". It does not exist, there is no centripetal force (on the refrigerator) for it to be a reaction to, and there is no 3rd law reaction whatsoever. There is no violation of Newton's third law because the force doesn't actually exist.

On a different note, as a matter of policy, we don't sign articles here, since they are not owned by any one person. It's also considered rude to completely replace an existing article, and is likely to get your changes reverted.

-- Cyrius|&#9998 00:23, Apr 13, 2004 (UTC)

Hello Cyrius: Thanks for responding. In reading through your explanations, I can see why it is that you think the misunderstanding lies within my work. Clearly we are applying the term "centrifugal force" in entirely different ways. The goal here shall be to learn which definition, your or mine, is the valid one. I think my definition may be found in the history log of "centrifugal force" posted on Wikipedia in early April, 2004.

Let us begin by looking at the term "centrifugal force".

The term "centrifugal force" was likely applied much earlier than Isaac Newton's time as an explanation for the behavior of objects on horizontal turntables such as a flopping pot on a potter's wheel or riders clinging to an amusement park merry-go-round or liquids being separated in a centrifuge. Later, Newton himself invented the matching term "centripetal force" to be applied to the inward-directed force he recognized as the action force causing the activity of "centripetal" acceleration present whenever an object is being forced to travel a curved path.

The term "Centrifugal force" tells us at least five things: 1) "Centri" (center of a curve or circle) tells us that an object (or portions thereof) is traveling a curved path where its motion is being turned aside from a straight-line path; 2) This turning aside represents a change in velocity which tells us that centripetal acceleration is present and directed toward the "Centri" of the object's curved path of travel; 3) Newton's LAW I tells us that the activity of this "Centri"-directed acceleration is always caused by a "Centri"-directed or centripetal action force; 4) "fugal" (fleeing from the "Centri") tells us that during the accelerational activity of this event, which is inward-directed toward the "Centri", the accelerating object experiences a force of some type (action or reaction) that is outward-directed away from the "Centri" of the object's inward-curving path of travel. 5) "force" tells us that this outward-directed "centrifugal force" represents a force (push or pull) impressed against or within the matter of the object for if it did not represent a force of some type there is no point in its use. In other words if no "centrifugal force" is impressed against or within the object's matter then there exists no reason to use the term. This is a scientific term we are debating. Applying a valid scientific term to nothing at all is scientifically unacceptable for it is not logical to waste a perfectly valid scientific term on what is for the object a non-event.

We both have access to these five characteristics of "centrifugal force" while developing our definitions. (I assume you are not a beginner since clearly you see yourself as capable of writing scientific definitions, a task far beyond the limited insight of a beginner.) If either one of us has chosen to ignore or oppose any of these five characteristics of the term "centrifugal force" then we do so knowing that such an ignoring puts our definition at risk of being less than true. Unfortunately, in the writing of definitions, any one thing less than true makes the whole definition false. Physics is a most unforgiving science in this regard.

I will summarize your definition and explanation first. In the first sentence of your definition you clearly state that "Centrifugal force" is not a force but an experience of an inertial force.... A requirement in writing any definition is clarity. By saying that "centrifugal force" "is not a force" but instead is "an experience of an inertial force..." it is not particularly clear as to what you are telling your definition's readers. I take the first half of this first sentence to mean that you think "centrifugal force" is not a force (push or pull) at all. So right away I see you have chosen to oppose characteristic #5 by applying the scientific term "centrifugal force" to an event where no such force is present.

Let's see if somewhere you explain how you see "centrifugal force" as being the "experience" of an observer watching a non-force "centrifugal force" event unfold. In the fourth paragraph of your explanation you state "Centrifugal force is the appearance, from your viewpoint at the center, that there is some mighty force trying to pull the bucket outward. This "force" is not real, has no 3rd law counterforce, and is caused by inertia's straight line effects in a rotating reference frame." (Note, the quotation marks around the word force are yours implying something other than a real force.)

We have both whirled a bucket about our person. Yet I came away with a different perspective of this accelerational event. We both recognize that as the observer, my frame of reference while focusing on the whirling bucket is rotating at an equal rate. But as an accelerating observer, apparently only I realize that my observation of both the (stationary) bucket and the whirling background objects is highly suspect and contrary to the truth of this event. It is clear to me that you think your observations as an accelerating (rotating) observer are every bit as valid as your observations that are made when no noticeable acceleration is occurring to your person. Let's see which position is right. If your position is right then the observations of an accelerating observer are as true as the observations of a non-accelerating observer. If my position is right then the observations of an accelerating observer are without merit as long as the accelerating observer chooses to ignore his or her rate and direction of acceleration (including rate of rotation) at the time of the observation which is the way you portray your accelerating observers.

When you whirl the bucket about your person, you see a stationary bucket in front of you. Behind the bucket you see a whirling background including a card table upon which I have placed a glass full of water. Since you see the bucket as stationary, it makes no sense to you that you have to impress a force on the rope in your direction just to keep the bucket from moving away. If you stopped impressing this action force against the bucket you think some mysterious "mighty force" will pull the bucket outward from your position. You see this "mighty force as imaginary or "not real". You also see "it" as having no inward-directed (opposing) force. Finally you tell your readers that this imaginary or unreal force has a cause! Again, clarity is important in a definition. At this point I am wondering how it is that this unreal nothing you think represents centrifugal force can possibly have a cause. How can nothing have a cause? In the end you do acknowledge that yours is a rotating (accelerating) frame of reference. But you do not mention that you think this in any way affects the validity of your observations. As far as you are concerned, the whirling bucket is at rest at the end of the rope and should need no force from your person to stay at rest. Meanwhile the whirling background is visibly orbiting you and the resting bucket. So from your perspective, any acceleration present belongs to the objects in the background as they whirl about you and the resting bucket.

There is one obvious problem. The surface of the water in the glass on the card table is continuing to remain flat as you observe the glass whirl about your position. This impossibility in a whirling glass of water whose surface remains flat means that something is very wrong with your observation. The glass appears to you to be experiencing centripetal acceleration yet the flat water surface does not reveal acceleration's presence. By now, despite what you think you are seeing, you conclude that the water must not be whirling about your person. Therefore you logically decide that it is your body that is rotating the other way making the glass appear to be accelerating when in fact it is not. This also explains why it takes a centripetal force from your hand to cause the bucket to whirl at the same rate of rotation as your body... making the bucket appear to be stationary when in fact it is not. At this point your realize that observations made while accelerating are without merit until you admit and take into account your rate and direction of acceleration as the observer.

Such merit-less observations are the basis of your misunderstandings regarding the reality of every rotating or orbiting object's centrifugal acceleration/Reaction force. An accelerating observer who insists on ignoring his acceleration while trying to determine the truth of an event will never arrive at that truth. He will remain forever confused. I refer to his state of mind as being influenced by Coriolis Confusion. An article on Coriolis Confusion is available at http://www.PhysicsNews1.com/question_14.html

Now that we see that trying to determine the truth of an event is hopeless while taking the role of an accelerating observer in denial of his acceleration, let's have a look at your refrigerator being carried upon a frictionless platform supported by a moving flatbed truck. When the truck's front wheels are turned left applying a centripetal action force to the chassis causing centripetal acceleration for the chassis, also to the left, it appears to the onboard observer that the resting fridge suddenly accelerates to a motion that carries it off the right side of the flat bed. The accelerating observer declares the fridge's apparent acceleration "centrifugal acceleration" and invents a Law I "centrifugal force" to account for the apparent "centrifugal acceleration". At this point our Coriolis observer is totally confused. Since he remains steadfastly in denial of his own continuing acceleration, he can think of no possible source of the "centrifugal force" so he ends up thinking the observed "centrifugal acceleration" of the fridge is real, which is a mistake, and that any reference to any centrifugal force is unreal, which also is a mistake. Sound familiar?

When I look at this event, I recognize that no horizontally-directed acceleration is occurring to the fridge, no matter who is looking at it. The non-accelerating observer at the side of the road sees the truth. The onboard accelerating observer does not see the truth. He remains fooled by what he sees to the end. His opinions and conclusions are based upon misunderstandings and therefore are opinions and conclusions without merit.

At the real event here, centripetal acceleration/Action forces measurably present at the front tires are pushing both right on the pavement and left on the chassis. In order to push left (inward) on the chassis with an external (contact) force, LAW III tells us that the chassis must push equally back or right or outward with an acceleration/Reaction force that is also measurably present. I, and many others see that this outward-directed centrifugal reaction force as the true centrifugal force whose recognition dates back to before Newton's time. While the fridge is not experiencing centripetal acceleration, the truck's chassis is, so the truth of this event is that the truck is being forcefully accelerated out from under the non-accelerating fridge. As with all accelerations, this centripetal acceleration is absolute. Meanwhile our onboard observer is hopelessly lost for he falsely believes that acceleration is a relative event. Worse yet, he steadfastly believes that his every observation is perfect, without any flaws to cast doubt over its perfection.

Your misunderstanding of centrifugal force is relatively modern and probably dreamed up by a group of inexperienced educators. In any case, as you can see, my understanding of the true centrifugal force present in this event meets all five of the characteristics of the term centrifugal force. Meanwhile your version meets with but one since the fridge is 1) not having its velocity changed, 2) is not experiencing centripetal acceleration, 3) therefore is not experiencing a centripetal action force, 4) is not experiencing a centrifugal acceleration/Reaction force, and finally, the one characteristic you predict to be true that actually is true is that 5) no outward-directed action force of any kind is affecting the fridge. (Remember that centrifugal force is always a reaction force and therefore can never be the cause of any outward-directed event. It only reacts to inward-directed events caused by inward-directed centripetal acceleration/Action forces.)

To read more about the concept of rest-motion, acceleration/Action and acceleration/Reaction forces, and much more, visit http://www.PhysicsNews1.com. Of course not everyone in the internet encyclopedia business agrees with your fictitious "force" conclusion. A visit to the infoplease science encyclopedia located at: http://www.infoplease.com/ce6/sci/A0811114.html will reveal that they recognize, as do I, that the centripetal action force is balanced by the centrifugal reaction force in perfect agreement with Newton's LAW III. Check it out.

As for the effect you are trying to label "centrifugal force", I think Coriolis Confusion is the proper term. It is a shame to waste the perfectly good Physics term centrifugal force on the nothingness of the Coriolis Confusion. To do so is to honor the confusions of an accelerating observer encumbered by denial.

Thanks for providing this format for our debate.

Ethan Skyler

P.S. If you would enjoy reading of another accepted concept of Physics that is completely imaginary, visit http://www.PhysicsNews1.com/article_1.html. You will be taken to an article entitled "The Reality of Newton's Inertia". Galileo's true role in the development of this concept, to the embarrassment of Newton, is explained near the end. This original article is a PhysicsNews1 exclusive. Enjoy!

It seems we have come down to a disagreement about labelling, but I can't be sure due to the sheer volume of your comment. You call for clarity from me, but do not do me the same courtesy, instead burying me under pages of text.

You also seem to be under the mistaken impression that I am the author of the article. The only editing I have done to the page is to revert your changes because I saw them as based on a misapplication of the label "centrifugal force". -- Cyrius|&#9998 17:17, Apr 27, 2004 (UTC)

I guess you could call this a disagreement in labeling. Currently the term centrifugal force is being defined as the "experience" of observing a non-accelerating object from an accelerating frame of reference. The validity of the observation should be questioned. The object is said to be accelerating when it is not. Further the imaginary "force" said to be "causing" this imaginary "acceleration" is labeled as "centrifugal force" which is then itself said to be fictitious or imaginary.

In truth, the label "centrifugal force" should be applied as follows:

Centrifugal Force The outward-directed reaction force that is present in every event where an object is rotating or orbiting about a central axis. This often measurable centrifugal acceleration/Reaction force is caused by the event's centripetal acceleration/Action force. As a reaction force, the centrifugal force provides equal and opposite support for the centripetal action force as predicted to exist by Isaac Newton's LAW III while serving in no manner to reduce or cancel the inward-directed acceleration. It merely goes along for the ride as an outward-directed reactionary support force that is always present during the inward-directed acceleration of an object's matter.

Ethan Skyler

PS This definition is close to but somewhat better than the definition posted in infoplease.com. I think it represents a good solid beginning. Modifications and improvements to this definition will take us further in the direction of the truth.

The articles in scientific journals are always signed by their authors even though the copyright is given over to the journal. Also the author is allowed to use his words in his own work as a condition of the copyright agreement.

Extending this practice to Wikipedia definitions can only enhance respect for the work presented here.

The whole point of calling it fictitious and imaginary is that the observers perceptions are suspect. In the rotating reference frame, one appears to see two forces (Centrifugal force and Coriolis force) which are not actually there. Assigning the label "centrifugal force" to the Newton's 3rd reaction to centripetal force removes a useful label for this phenomenon.

As to the signing of articles, it is a matter of Wikipedia policy that articles are not signed, because articles may be freely edited by anyone. Signing would discourage this. -- Cyrius|&#9998 17:09, Apr 28, 2004 (UTC)

Overall it is not right to apply a Physical term to an observer's experience. This is an area outside the science of Physics. The problem is that you have chosen a real Physical term that is needed elsewhere in reference to a very real, often measurable, LAW III reaction force. I think the solution is to find a Psychological term to apply to the accelerating observer's tendancy to develop suspect observations. I think something like "Coriolis effect" in reference to the accelerating observer's confusion would be better.

I think the ultimate solution is education. Educators need to explain the problems associated with accelerating observations. The students need to be told that, for example, that the truck's observer is confused by what he sees. The students will be empowered to recognize that no acceleration is occurring to the fridge as the truck accelerates out from under it. No acceleration means no acceleration-causing force is present. Then when the cause of this event needs explaining, the centripetal acceleration/Action force of the truck's front wheels provide the LAW I approved answer to the truck's centripetal acceleration. It all makes sense to the student and is easier on the teacher.

What do you think? Can we have "centrifugal force" back so that it may be used where it is really needed?

Ethan Skyler

You may be right that the term is in need of a renaming, but Wikipedia is the wrong place to go about that change. The usage I have chosen is the one used by physicists, engineers, and especially meteorologists who must deal with the constantly rotating reference frame of the Earth. The engineering dynamics textbook sitting in the next room from me makes enormous reference to centripetal force and 3rd law reactions, but does not even have an entry for "centrifugal force" in the index.

In all cases when I was exposed to it at the high school and university levels, the description came with the clear explanation that the force in question does not actually exist, and is a figment of misinterpreting the rotating reference frame.

Applying the label "centrifugal force" to the 3rd law reaction to centripetal force would not be useful, as that force is more usefully described as the reaction to centripetal force. Labelling the observer-dependent fictional force is far more important, as overcoming the incorrect intuitive understanding of it is an important step in the teaching of classical mechanics.

-- Cyrius|&#9998 04:18, Apr 29, 2004 (UTC)

There is a clear difference between your centrifugal force experience and my centrifugal force reaction to centripetal force. That difference is that your centrifugal force is mistakenly thought to be an outward-directed event causing action force. Such as the potter who declares that "centrifugal force caused my large soft pot to rip apart at the rim and flop on the turning wheel." Here he expects that some outward-directed action force is responsible. The truth is that the pot's soft rim was unable to continue supplying the tension-based inward-directed centipetal action force necessary for the rim's matter to continue its centripetal acceleration.

The term centrifugal force is too broad a brush, covering up any mention of the reaction-to-the-action of centripetal force. Your imaginary force could logically be called "centrifugal action force" which all experts will agree does not exist. My real force could logically be called "centrifugal reaction force" which all experts would agree does exist. This way room to exist is granted to the real centrifugal reaction force.

The Wiki definition does use the action word "acting" for the imaginary centrifugal action force supporting this dual naming I propose. But what of that "equal in magnitude" to the centripetal action force part? What's with that? Please explain.

Stop referring to my usage of the term "centrifugal force" as if I have invented it. I am using the standard definition, as defined by people who work within rotating reference frames on a regular basis. If you want to redefine the term, you need to start somewhere other than Wikipedia, as that is not its purpose. -- Cyrius|&#9998 16:04, Apr 29, 2004 (UTC)

How does this compare to Centripedal force - I seem to recall that centrifugal wasn't what it was commonly thought of (tendancy for spinning things to push outward)??

Rewrote, with pseudo-force explanation included.

I think the confusion with centrifugal should be pointed out (and 213.253.39.xxx did this pretty well), but not with the term 'pseudo-force'. It is a valid, normal force, it is the misunderstanding that lots of people have with it that is the problem.

Also slightly unhelpful is:

Centrifugal force is not actually a force in the same way as magnetic force or gravity

Of course it is - it is even carried by gravitons (if they exist.) It is just how the force arises that is different. -- sodium

An observer with a rotating frame of reference matching that of the container could also view this as motion under Newton's laws, with the addition of the centrifugal pseudo-force as a force to be resisted by the container.

I don't think this actually says anything more than already stated in the last paragraph. -- sodium

Physicists commonly disrecommend speaking of centrifugal forces instead of centripetal forces, because many people draw wrong conclusions from the idea of a centrifugal force. For example, many are not aware that a hammer released by a hammer thrower continues to move in a straight line (in the non-rotating reference frame), tangentially to its previous orbit, and its flight path is only influenced by gravity and friction. Also, the movement of this hammer in the rotating frame of reference, that was used to describe its orbit, could not be explained by centrifugal force. Whereas the model would make one expect a straight movement away from the center of rotation, with radial velocity increasing linearly with time, the hammer would instead, in the rotating reference frame, move spirally, with a radial velocity that converges toward a maximum (its velocity in the associated inert reference frame).

Removed the above as it seems to confuse the article and I didn't understand what it was trying to say. Rjstott 03:58, 4 Apr 2004 (UTC)

Vector Definition

The definition of a vector is a quantity which adds according to the parallegram law. There are quantities that have orientation and magnitude but that are not vectors.

Pud 03:36, 22 Aug 2004 (UTC)

I'm not a physicist or anything like that, but a few things appear to me to be ignored in all of this discussion. It is for certain that the term "centrifugal force" is commonly used to describe a force acting upon an object such as a car cornering or a ball attached to a string. It is also certain that this use of the term is incorrect as those objects experience only centripetal forces. Newton's third law means that there will be an opposite force to this centripetal force acting upon another body (not the objects mentioned) In the case of the string this force would be the tension pulling against the hand holding the string - in the case of the car this force would be the component force exerted by the accelerating car against the ground. Some people here are claiming that in the case of the string it would be correct to call this reactive force a centrifugal force - as it is opposing the centripetal force. If this was correct that would mean that in the case of the car, the car experiences centripetal force and the road/planet experiences centrifugal force. It seems amusing to think that I'm imparting centrifugal force to the planet when I take my car into a bend - but this is certainly never how you would hear this term being used. It would appear then that the idea of using the term centrifugal force to describe the reactive force is inappropriate and best avoided as it is in most modern physics texts.

The term "centrifugal force" is best defined as a mechanical engineering misnomer.

When an object being rotated causes something to be thrown to the outside - such as water in a spin dryer the effect that would be commonly termed "centrifugal force" is an illusion. The water is ejected because it travels effectively in a straight line and it is the absence of centripetal force that causes it to leave the cylinder - not "centrifugal force".

IN this case the term "centrifugal force" is best described as an illusion. as there is no "centre -fleeing" (latin derivation) force at all.

Huygens was the first to formulate centripetal acceleration - but got it in the wrong direction - believing that it was away from the centre. Just because errors like this were made over 300 years ago does not mean that they have to be continued today.