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PhDeezNutz
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Vanadium 50 said:Why not rename resistance to voltage? Why not rename force to energy?
Why not call everything "Bruce", just to prevent confusion?
Vanadium 50 said:Why not rename resistance to voltage? Why not rename force to energy?
Why not call everything "Bruce", just to prevent confusion?
I think you may well have something there. It does rely on teachers having a higher level of Science knowledge, though.bob012345 said:Who says we must be slaves of old confusing terminology? Langauge changes. New students won't be confused.
In this case, I don't see any confusion. Centripetal and centrifugal forces are well-defined for centuries.bob012345 said:Who says we must be slaves of old confusing terminology? Langauge changes. New students won't be confused.
No, I was suggesting changing the name of the latter to the former because that's the more common word in people's minds. It was a sort of tongue in cheek but also half serious comment.Vanadium 50 said:Are people arguing that centrifugal and centripetal force are the same thing and the two names are what's confusing? That is not the case.
I doubt changing the names would do anything besides increasing confusion. Of which there is already plenty.bob012345 said:but also half serious comment.
There is also the matter of the 3000yr etymology of the word from Latin centrum (see center) + -fugus ‘fleeing’ (from fugere ‘flee’). This is just ridiculous.bob012345 said:No, I was suggesting changing the name of the latter to the former because that's the more common word in people's minds. It was a sort of tongue in cheek but also half serious comment.
Does that really matter in the grand scheme of things?hutchphd said:There is also the matter of the 3000yr etymology of the word from Latin centrum (see center) + -fugus ‘fleeing’ (from fugere ‘flee’). This is just ridiculous.
Depends on your frame of reference.sophiecentaur said:It leaves on a tangent and is not 'thrown outwards', as school kids had been told by generations of non-physicists.
Why do we call an inertial frame one that does not have inertial forces but a non-inertial frame is one that does?jbriggs444 said:Depends on your frame of reference.
Viewed from the rotating frame, it begins accelerating radially outward. But then begins curving due to the addition of Coriolis to the centrifugal force.
Viewed from an inertial frame, it moves tangentially in a straight line as the platform accelerates away in its circular path.
Why do we drive on a parkway and park on a driveway?bob012345 said:Why do we call an inertial frame one that does not have inertial forces but a non-inertial frame is one that does?
Of course it does. But a school student is standing, looking at the event and frames of reference are not dealt with early on in school. Just ask a kid to draw a spinning disc and what will happen to an object when released from the edge. 100:1 they will draw a radial line (or a curve). This is the level that we're (I'm) dealing with and, to my mind, forbidding centrifugal force is forgivable at that stage. Using the concept of a fictitious force could turn the whole business into magic and we don't want that.jbriggs444 said:Depends on your frame of reference.
In my experience the main confusion comes from not clearly distinguishing centrifugal force (an "inertial force", only present in the description of the motion in a non-inertial frame) and centripetal force (a "true force" occuring in the description of the motion in a non-inertial frame).Vanadium 50 said:Are people arguing that centrifugal and centripetal force are the same thing and the two names are what's confusing? That is not the case.
Why is "velocity" relative, but "velocity relative to X" absolute?bob012345 said:Why do we call an inertial frame one that does not have inertial forces but a non-inertial frame is one that does?
The wheel acts by centripetal force on Bond. But then, by the 3rd Newton law, Bond acts on wheel by the opposite force. Isn't this opposite force the centrifugal force?kuruman said:Some of you have seen this already when a similar discussion flared up and I apologize for the repetition. I resisted at first, but it is worth reviving because it encapsulates the controversy well.
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The latter is absolute precisely because it's relative.A.T. said:Why is "velocity" relative, but "velocity relative to X" absolute?
That opposite force is sometimes called the "reactive centrifugal force". It is not, of course, the same as the inertial "centrifugal force" that is most often meant by the phrase.Demystifier said:The wheel acts by centripetal force on Bond. But then, by the 3rd Newton law, Bond acts on wheel by the opposite force. Isn't this opposite force the centrifugal force?
But if it quacks like a duck . . . . . Those two forces have the same values and would have the same visible effect (wherever you're looking from).jbriggs444 said:That opposite force is sometimes called the "reactive centrifugal force". It is not, of course, the same as the inertial "centrifugal force" that is most often meant by the phrase.
They do in some cases. Not all. The inertial centrifugal force continues to exist (in the rotating frame) even after the string breaks or the centrifuge explodes or the car hits a patch of black ice. The reactive centrifugal force ceases to exist when the string breaks, etc.sophiecentaur said:But if it quacks like a duck . . . . . Those two forces have the same values and would have the same visible effect (wherever you're looking from).
That's because of the apparently curved / zig-zag path seen by Mr. Bond? Sounds very non-Newtonian, though.jbriggs444 said:The inertial centrifugal force continues to exist (in the rotating frame) even after the string breaks
Archimedian spiral, approximately. It is Newtonian -- provided that you ignore the third law. Inertial forces such as centrifugal and Coriolis are not interaction forces. They have no third law partners.sophiecentaur said:That's because of the apparently curved / zig-zag path seen by Mr. Bond? Sounds very non-Newtonian, though.
Well put. And something else to confuse young minds with - just after they learn to distinguish between third law pairs and forces in equilibrium.jbriggs444 said:Archimedian spiral, approximately. It is Newtonian -- provided that you ignore the third law. Inertial forces such as centrifugal and Coriolis are not interaction forces. They have no third law partners.
As the cartoon suggests, perform a coordinate system transformation and force-like effects pop out.
I very well remember that a prof told me the same. "This is not a force!"Argonaut said:I've just come across the following line while studying (Young & Freedman) and found it amusing.
It sounds like a dirty family secret we discuss once and then should never mention again
You can't - that's kind of the point. You can measure things that (in a rotating frame) you might call a reaction to a centrifugal force, but you cannot measure the centrifugal force itself.Omega0 said:If it feels phyisically like a force and I could measure it as a force
It doesn't. When analyzing from a rotating frame, the inertial centrifugal force applies to everything that is not on the frame rotation axis. Even to things that are perfectly inertial and definitely don't "feel" any force. It's just there to make the accelerations in the rotating frame consistent with Newtons 2nd Law, not to explain any deformation or stresses.Omega0 said:it feels phyisically like a force
As others have said, you cannot feel or measure an inertial force like the centrifugal force. All that you can do is to infer it through the motion of the object wrt some frame given all of the directly measurable real forces.Omega0 said:If it feels phyisically like a force and I could measure it as a force it is force - for me.
I am speaking about local measurements in spacetime. Is it just wording?Ibix said:You can't - that's kind of the point. You can measure things that (in a rotating frame) you might call a reaction to a centrifugal force, but you cannot measure the centrifugal force itself.
But that is a mistake. A careful analysis will show that you are moving inertially while not in contact with the cylinder - you move in a straight line.Omega0 said:You jump and you fall back. You call it, whyever, centrifugal force.
Well, gravity is another thing you can't measure. You can measure the force from the floor on your feet (that's what a weighing scale does), but when you are in free fall there is no detectable force. That's a key insight (the equivalence principle) on the road to general relativity.Omega0 said:In other topologies you may have called it gravitation, which I can measure,
It is not just wording. It is a matter of experiment. There is no physical experiment you can make to actually measure an inertial force. You can only infer it from the acceleration combined with measurements of all of the real forces.Omega0 said:Is it just wording?
I.e. you infer the force from your motion.Omega0 said:You jump and you fall back.
Just to expand on that, you can infer from the changing relative motion between you and the floor that there's a force on at least one of you and the floor. And accelerometers attached to the floor will read non-zero while those attached to you read zero. Conclusion: there's a force on the floor and it's accelerating, you are inertial.Dale said:I.e. you infer the force from your motion.
Ahhhh I got it, sorry. Absolutely right. Thanks. Maybe I watched too many movies where I thought afterwards that rotation is a nice alternative to gravitation but it is not. So clear. My fault.Dale said:You cannot measure it in any other way. It does not produce a reading on an accelerometer or a strain gauge or anything else you can think of. While you are only under the influence of that force all local experiments will be the same as in free fall far from gravity.
Centrifugal force is the apparent force that seems to push an object away from the center of rotation. Physicists cannot mention it because it is a fictitious force that only appears to exist in a rotating frame of reference.
Centrifugal force is often taught in introductory physics courses as a simplified explanation for the motion of objects in a rotating frame of reference. However, as students progress in their studies, they learn that it is not a real force and should not be mentioned in scientific discussions.
No, centrifugal force and centripetal force are not the same. Centripetal force is a real force that acts towards the center of rotation, while centrifugal force is a perceived force that acts away from the center of rotation.
No, centrifugal force cannot be measured because it is not a real force. It is simply a perceived force that appears to exist in a rotating frame of reference.
In practical applications, such as designing amusement park rides or understanding the motion of objects in a rotating space station, the concept of centrifugal force can be useful as a simplified explanation. However, in scientific discussions and calculations, it should not be mentioned or considered as a real force.