Talk:Centrifugal force

Talk:Centrifugal force/Archive 1

--Cleon Teunissen 09:42, 18 Jan 2005 (UTC)

I have replaced the article on centrifugal force with a new article. The first section is written with people with very little physics background in mind. As the article goes on, the level increases.

Most of the article is aimed at explaining why centrifugal force is so confusing. The dynamics of rotation is counter-intuitive. It would already be confusing with only newtonian dynamics around, but inevitably people start invoking relativistic dynamics, multiplying the confusion. Relativistic dynamics views centrifugal force the same as newtonian dynamics does, but not discussing relativistic physics would allow people room to assume that relativistic physics has not been taken into account. --Cleon Teunissen 09:42, 18 Jan 2005 (UTC)

Smyth has done some essential cleanup. Thanks! --Cleon Teunissen 11:56, 18 Jan 2005 (UTC)

Duk, thanks for correcting the spelling. Actually, I spelled physically on purpose with 'ph', referring to Physics. But *pedia articles are not the place to use non-standard spelling. Cleon Teunissen 21:16, 22 Jan 2005 (UTC)

Contents

1 "Centrifugal force" is not a force 2 Newton's third law of motion 3 Rewrite of the article, 30 jan 4 How circular motion is to be understood

"Centrifugal force" is not a force

A centripetal force acts to keep the object in circular motion, and a reaction force is imposed on whatever is providing the centripetal force.

"Centrifugal force" is not a force - it is just inertia. 210.50.105.53 09:00, 13 Jun 2004 (UTC)

"Physics teachers are keen to teach that the real force is centripetal force and that centifugal force is the reactionary force which balances it. Conversion of angular momentum into linear momentum is used in a number of ways, the most obvious is perhaps a sling."

What does that mean? Maybe the second part is right, but the first part is (hopefully) incorrect. 210.50.105.53 09:11, 13 Jun 2004 (UTC)

My dictionary (Webster New World, 1968) says that "Centrifugal force" is a force. Duk 16:11, 25 Sep 2004 (UTC)

(William M. Connolley 11:24, 18 Oct 2004 (UTC)) Is it a force...? Firstly, your dictionary isn't going to help. Its harder than that. See-also the talk (and text) at Coriolis force. If Centrifugal force is just inertia, is gravity the same? Unless you can define a force in such a way as to make the question meaningful, I think the answer is going to be "depends on your POV".

(Rsduhamel 20:53, 28 Nov 2004 (UTC)) Saying centrifugal force doesn't exist is like saying there's no such thing as a Sparrow Hawk because it's official name is American Kestrel. Centrifugal force is what people call the sensation of an outward force exerted by a spining object. It's just what people call something that feels real to them. I think the article explains it well. If we are going to say centrifugal force doesn't exist then let's stop calling a Sunrise a Sunrise and call it what it really is ("My, what a beautiful Earth rotation we're having this morning.").

Prof. Enrico Lorenzini (of Harvard) and Prof. Juan Sanmartin (of the Polytechnic University of Madrid) have an interesting discussion on this in the Dec 2004 issue of Scientific America;

In response to a snide letter objecting to them using the term to describe a force; they reply "... yes, professors shy away from teaching first year physics students this term ... yes it is a valid concept when used within a rotating frame of reference..." (paraphrased). Duk 03:13, 29 Nov 2004 (UTC)

I think the professors that avoid using the term to an audiance of first year physics students are right. A rotating reference frame isn't a valid concept. However, it is quite useful physics shorthand. In teaching physics I would never use the phrasing that 'the comet Levy-Shoemaker was ripped apart by tidal forces', but in conversation between experienced physicists I would readily use 'tidal forces' as an abbreviation. Cleon Teunissen 09:42, 24 Jan 2005 (UTC)

Newton's third law of motion

Cleon Teunissen 16:23, 12 Jan 2005 (UTC) Newton's third law of motion deals with conservation of linear momentum.

If you have two objects exerting a force on each other, for example a repulsive force, then as soon as you let them go they will fly away from each other, but their common center of mass will remain in the same spot (or will continue in the same straight line, if it was moving in a straight line.)

Newtons third law of motion does not refer to objects that remain solid.

(William M. Connolley 19:43, 12 Jan 2005 (UTC)) I dislike the distinct in the article between "action forces" and... something else. I doubt it means anything. I think CT is right that the reference to Newtons 3rd law is wrong. This needs thinking about...

Cleon Teunissen 22:08, 12 Jan 2005 (UTC) As I mention in my proposal for revision: the Newtonian description of the dynamics of circular motion is highly counter-intuitive. To many people, the newtonian description feels wrong. I think that is the main issue.

Rewrite of the article, 30 jan

I have rewritten the article. The first section is written for people with no phyisics background at all. The first section aims to stay as close to everyday experience of motion as possible.
As the article goes on, the level increases.
The final sections assume that the reader has a lot of physics knowledge. Cleon Teunissen 07:04, 30 Jan 2005 (UTC)

How circular motion is to be understood

202.156.2.82 wrote:

The centrifugal force may be understood as arising from the tendency of the stone to move in a straight line, or a path tangential to its position on the circle.

I have removed this remark because it leads to an inconsistency. If there would be a centrifugal force then the centripetal force would be prevented from maintaining the circular motion. The circular motion is maintained, so there is only one force at play: centripetal force.

Because of inertia a force is required to make an object deviate from moving in a straight line. Manifestation of inertia opposes the centripetal force, but it does not prevent the centripetal acceleration.

Without inertia, objects would be instantly accelerated to lightspeed. Because of inertia acceleration is proportional to the exerted force. The bottom line: inertia is not a force. Inertia involves opposition to change, but inertia never prevents the change. --Cleon Teunissen | Talk 14:49, 22 Apr 2005 (UTC)