Re: Centrifugal force

["Kilmer, Skip" <kilmers@GREENHILL.ORG>]

Thanks, Joe. Let me see if I understand. Suppose a conical pendulum with no friction or air drag. The "centripetal force" on the ball is the horizontal component of the string pulling it inward. The "centrifugal force" on the string is opposite to the centripetal force on the ball, and acts to pull outward on the end of the string. Ball and string (c.o.m.) have different accelerations because each has a different mass and different other forces acting on it. Is that what you're saying?
I thought earlier posts were implying a centrifugal force on the ball, which exists only in a frame of reference rotating with it, resulting from the ball's inertia.
skip 

-----Original Message-----
From: Joseph Bellina [mailto:jbellina@SAINTMARYS.EDU]
Sent: Monday, November 17, 2003 11:07
To: PHYS-L@lists.nau.edu
Subject: Re: Centrifugal force


A number of folks have responded to this well.  I just want to point out
that will due respect, your question implies that you may be confusing
issues having to do with the second law, the forces acting on a single
object, and the third law, equal but opposite forces acting on different
objects.
This is a common problem for students, and shows up often through the
use of the words "equal and opposite" that has a very different meaning
in the context of the 2nd law than it does in the context of the third.

It is a good question to ask ourselves and our students to be sure we
understand the conceptual difference.

cheers,

joe

On
Mon, 17 Nov 2003, Kilmer, Skip wrote:

> I've never really understood Physics teachers' distaste for the phras=
> e, centrifugal force. Doesn't N3 tell us that for every centripetal f=
> orce on an object there is an equal centrifugal force on another obje=
> ct?
> skip=20

Joseph J. Bellina, Jr.               574-284-4662
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556