Re: physical pendulums

[Bob Sciamanda <trebor@VELOCITY.NET>]

Herb, I think you are confoosed!

The center of oscillation (defined only with respect to a given suspension
point in the body) is that point which, when used as the point of
suspension, gives the same period of small amplitude oscillations. That is
not the question asked.


Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

----- Original Message -----
From: Herbert H Gottlieb <herbgottlieb@JUNO.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Wednesday, September 22, 1999 11:15 PM
Subject: Re: physical pendulums


> On Wed, 22 Sep 1999 19:30:53 -0700 fred brace <fredb@TELEPORT.COM>
> writes:
> > I am using a set of physical science lab materials on the pendulum.
> > One of  the activities asks the students to get a washer, a bolt and a
> long
> > wooden  dowel to swing with the same frequency. It says that if the
> center
> > of  masses line up, then the pendulums will have the same frequency.
Is
> > this true?
>
> This is almost true, but not quite true.  For a uniform wooden dowel,
the
> center of mass is at
> the center of the dowel.  It's "center of oscillation" is located at
> distance equal
> to 2/3 of its length , measured from its point of suspension.   Thus a
> simple pendulum
> consisting of a uniform steel washer at the end of a string of
negligible
> mass
> would have the same frequency as the swinging wooden dowel if the length
> of the
> simple pendulum is 2/3 as long as the dowel.  This is explained in
detail
> in most of the
> popular physics books for introductory physics.
>
> Herb Gottlieb from New York City
> (Where Professor Zemansky of our City College did a great job
> explaining this in his College and University  Physics testbooks).