Re: MOMENT OF INERTIA

[Jerome Epstein <jerepst@WORLDNET.ATT.NET>]

> If you have leaned forward, you have moved your center of mass.  If you
> were able to rotate your body without an outside force, you would be
> violating conservation of angular momentum.  Ask any astronaut!
Sorry must disagree. If you lean the upper half of your body forward and
your legs go backward then your CM will not move.
On the rotational part. You are able to change the orientation of your
body, though not the angular momentum. If you start at rest, stretched
out in the "up and down" direction", you can rotate the upper half of
your body, say clockwise, a bit by rotating your lower half the other
way. ANgular momentum stays zero. Then you can stretch out in the
"east-west" direction, bringing both halves of your body to rest.
ANgular momentum remains zero. One part of your body can exert a torque
on another part, but the total angular momentum of both parts cannot be
changed by internal forces. YOu can swing your arm, but your body will
rotate the other way.
J. EPstein