Re: MOMENT OF INERTIA

[Bob Sciamanda <trebor@VELOCITY.NET>]

The force of static friction in the rolling wheel performs much the same
function as does the force of static friction between your foot and the
floor when you walk.  Think of a wheel as the limit of an infinite number
of spokes, each with a shoe at its distal end!

Bob Sciamanda
Physics, Edinboro Univ of PA (ret)
trebor@velocity.net
http://www.velocity.net/~trebor
-----Original Message-----
From: Martha Takats <mtakats@ACAD.URSINUS.EDU>
To: PHYS-L@LISTS.NAU.EDU <PHYS-L@LISTS.NAU.EDU>
Date: Friday, December 18, 1998 2:30 PM
Subject: Re: MOMENT OF INERTIA


> Dan M's energy-conservation derivation is the one I use (so I don't
> have to worry about rotation about a moving axis, or an axis that
> isn't through the center of mass, etc.). But I still worry about why
> there are no non-conservative forces doing work--for example the force
> of static friction, which prevents slipping. Can anyone give a SIMPLE
> explanation of why we don't have to include it in the work-energy
> equation?
> We have a nice demonstration in which we use the Cenco wooden disk and
> brass hoop (same mass and radius) together with two Pasco 2.2-m dynamics
> tracks set up in the front of the lab. The students can verify that the
> masses, radii, inclination, starting point are the same, predict which
> object will win the race, then run the race. Very effective.
> --
> Martha Takats
> Department of Physics and Astronomy
> Ursinus College
> Collegeville, PA 19426