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When did centrifugal force die?

  1. Apr 24, 2008 #1
    Sometime in the mid-nineteenth century centrifugal force fell from grace with modern physics. Physics texts from the 1920’s define it, even apply it, yet modern texts ignore or deny it.

    Newton, Mach, Berkeley and Einstein all used centrifugal force to describe a force that seeks to “flee the center” in a rotating mass.

    Today, “centrifugal force” appears to have become a bad word in the physics classroom. It is ignored in modern texts, or it is mentioned in denial of its existence.

    A search of the Internet shows many authorities split on centrifugal force. Some use the term centrifugal force, while others do not. Some say that it was only a misunderstood centripetal force all along.

    I find it hard to believe the four gentlemen I’ve cited above could have had such a misunderstanding about the subject, yet I’m in no position to argue with the modern authorities who think otherwise.

    Apparently, there has been a change in thinking and centrifugal force has fallen from grace by many scientists. Can anyone shed light on when this rethinking occurred, and what may have catalyzed it. Do we now look at Newton, Mach, Berkeley, and Einstein as having been incorrect in applying centrifugal force in their work?
     
  2. jcsd
  3. Apr 24, 2008 #2

    LURCH

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    I don't think that the fellows you mentioned misunderstood the phenominon or its causes at all, but they probably did understand the value of communication. I'm sure they mostly used the term as a convenience, just because that is what people were generally calling it. Centrifugal force is not really a "force," in the strictest sense, it is just a special case of inertia. Nowadays, it seems that the inprecise terminology of the past is comnig back to haunt many fields of scientific research, in the form of erronious preconceived notions. So, I thinkthe community in general is a bit more touchy about misleading names. But that's just my opinion, though.
     
  4. Apr 24, 2008 #3

    Dale

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    To make matters worse, there are two distinct useages of the term "centrifugal force". The usual use is the inertial force on a body which is stationary in a rotating reference frame. The other, less common use, is the real 3rd-law "reaction" force to a centripetal force (e.g. if a string exerts a centripetal force on a ball then the ball exerts a centrifugal force on the string).

    Neither concept is so useful that it is worth the pedagogical trouble of trying to overcome all of the confusion needed to use them in a basic physics classroom.
     
  5. Apr 24, 2008 #4
    Reference frames. Rotating reference frames use a centrifugal force. However, it is still a pseudo-force.

    http://xkcd.com/123/
     
  6. Apr 24, 2008 #5
    There's a very good reason not to use the term "centrifugal force" in Newtonian mechanics. As a force, it's inconsistance with Newtonian mechanics, like Poop says more or less.

    There's a good reason for deriding it. You have students with false impressions that need corrected. A good text will tell you it's a pseudo force, and why, and eventually where it's a convenient utilitarian fiction.
     
    Last edited: Apr 24, 2008
  7. Apr 24, 2008 #6
    What's 'inertial force'?

    "Centripedal" comes from "center walking," or "walking to center" "Centrifugal" is "center fleeing" where "fleeing" is my word for "taking refuge from."
     
  8. Apr 25, 2008 #7
    Force resulting from the acceleration of a massive object. The measure of an objects resistance to changes in motion that is opposite to the change in motion i.e. a measure of force due to the properties of inertia. It is also a "pseudo" force.
     
  9. Apr 25, 2008 #8
  10. Apr 25, 2008 #9

    Doc Al

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    You've got to be pulling our leg! Centrifugal "force" is hardly ignored--it is essential in understanding how to view things from a rotating frame, something that is extremely useful. Pick up just about any intermediate mechanics book for an exhaustive discussion of noninertial frames and the resulting "fictitious" forces such as centrifugal and coriolis.

    Centrifugal force is ignored in first year physics classes, and rightly so. Students are just learning the concept of force and Newton's laws within inertial reference frames; adding the complication of "fictitious" forces due to noninertial reference frames would only confuse things. And one must distinguish "real" forces from noninertial forces.
     
  11. Apr 25, 2008 #10
    Unfortunately it is often also denied.

    In any case, history of centrifugal force could be interesting. It seems that after some people decided that it is too confusing for young students, some other people went into more extreme pedagogical policy, and started claiming that the concept is fundamentally incorrect.
     
  12. Apr 25, 2008 #11
    If we want to strictly follow Newton's laws then there is no centrifugal force (at least in inertial systems). However only a small conceptual adaptiation of Newton's laws defines centrifugal force:

    F=m*a

    F-m*a=0

    F+F*=0

    In this model each object resists acceleration with the force F*=-m*a and the sum of all forces is 0. However the force F* must still be considered different from external forces, since it must not be included in 1. and 3. law.
     
    Last edited: Apr 25, 2008
  13. Apr 25, 2008 #12

    arildno

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    "Centrifugal" means just "away from the centre".
    Of course, "real" forces might on occasion have a centrifugal contribution, the typical case being a mass attached to a rotating spring (not laterally bendable).
    The mass will typically oscillate around its equilibrium position; whenever the spring is slightly compressed, it will impart a centrifugally acting force upon the mass, driving it beyond the equil. position, when the spring will start acting centripetally upon it.
     
  14. Apr 25, 2008 #13

    Dale

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    Expanding on robertm's comments. The term "inertial force" is the same as "fictitious force", "pseudo force", or "d'Alembert force". The most common term is "fictitious force", and I just use the term "inertial force" because some people on this forum object to the characterization of them as "fictitious".

    If you are trying to do physics in a non-inertial reference frame (e.g. rotating reference frame) you will find that objects that are not under any force will accelerate. Therefore we introduce these fictitious forces in order to explain the acceleration.
     
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