Re: MOMENT OF INTERTIA

["James W. Wheeler" <jwheeler@EAGLE.LHUP.EDU>]

Perhaps you should consider the kinetic energy of the ring-disk.  For the
disk the inner parts move less rapidly than the rim.  Hence the
translational speed of the disk can be higher because a smaller fraction
of the gravitational energy gained by moving down the ramp in needed to
make the disk rotate.  (Note that the increased mass means both more
potential energy, more translational Kinetic energy, and more rotational
kinetic energy, all in proportion.  It is the distribution of the energy
that changes.)

On Thu, 17 Dec 1998, David Abineri wrote:

> Another question from a high school student:
>
> If one starts with a hoop and thinks about gradually filling in the
> inside of the hoop with mass until it eventually looks like a disk, one
> is certainly increasing the moment of intertia of the object. The effact
> of the above transformation is to produce an object which will roll ever
> faster down a given incline. I can show this easily mathematically but
> is there an intuitive way of explaining why this happens? My students
> understand the mathematics but seem to need a non mathematical argument
> too.
>
> Any help is appreciated.  David Abineri
>
>
> --
>  David Abineri   dabineri@choice.net