Re: [Phys-l] A ball at the center of a planet

["LaMontagne, Bob" <RLAMONT@providence.edu>]

I think we need the problem to be defined a little better. Does solid include "deformable". If so, how is the radius measured, i.e., along a radius from the center of the earth, tangent to it, an average, etc....?

Bob at PC

> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of William Robertson
> Sent: Monday, October 04, 2010 11:05 AM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] A ball at the center of a planet
>
> Ummmm.... trick question? Because of tidal forces, the ball is not
> truly a sphere at the surface of the planet. Or if the ball is a
> sphere at the surface, then the lack of tidal forces at the center
> mean it won't be a sphere there. New to this listserv, so I figured my
> first post ought to be something that's probably wrong. ;o)
>
> Bill
>
>
> William C. Robertson
> Bill Robertson Science, Inc.
> Stop Faking It! Finally Understanding Science So You Can Teach It.
> Woodland Park, CO 80863
>
>
> On Oct 4, 2010, at 8:43 AM, Fakhruddin, Hasan wrote:
>
> > Greetings folks!
> >
> > Here is a question for your intellectual entertainment:
> >
> > A solid rubber ball has a radius of r in vacuum at the surface of a
> > planet that is a solid uniform sphere.  The ball is now placed in
> > vacuum at the center of the planet.  Will the radius of the rubber
> > ball
> > (a) Increase
> > (B) Decrease
> > (C) Stay the same?
> >
> > Thanks
> >
> > ~ Hasan Fakhruddin
> > Instructor of Physics
> > The Indiana Academy for Science, Mathematics, and Humanities
> > Ball State University
> > Muncie, IN 47306
> >
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