Re: MOMENT OF INERTIA

[Mervin Koehlinger <tchkoehlimw@CRF.CUIS.EDU>]

On Sat, 19 Dec 1998, Jerome Epstein wrote:

> Obviously we are talking past each other. What do you mean "by launching
> upwards"? I imagine you mean pushing against something, such as a
> platform. Then (by the 3rd law) there is a force on your body from
> outside your body. It is this force that allows your center of mass to
> move. If you are free floating in space, you CANNOT move your center of
> mass. This is surely elementary.

Nor can you begin to spin; nor can you fall forward, which in one sense is
the same thing as spinning.

> When you "launch upwards" by pushing against something, that something
> "launches downwards", the CM of the whole system does not move.
> J. EPstein

Agreed.

Mervin Koehlinger
Physics Instructor
Concordia Lutheran High School
Fort Wayne, Indiana