Re: A weighty subject

[Bob Sciamanda <trebor@VELOCITY.NET>]

OK, I'll rush in and do what looks simple and non-controversial, namely
part a):

F_g = GMm/R^2(1-1/9) = (GMm/R^2)*(8/9) , directed toward the center of the
closest planet.  Next!

Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

----- Original Message -----
From: John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Friday, October 15, 1999 12:23 PM
Subject: Re: A weighty subject


> I've proposed exercises that I thought might reveal some conceptual
> difficulties previously in this thread.  Nobody took me up on them, so
> maybe I shouldn't bother trying to do it again.  Nevertheless, undaunted
> ...
>
> Consider two identical, spherically symmetric, nonrotating planets of
> radius R and mass M orbiting their common center of mass in a circle of
> radius 2R (and don't worry about Roche limits and all that!)
>
> a) What is the Newtonian "force of gravity" on an object of mass m near
> the surface of one planet when the other is directly overhead.
>
> b) What would a properly functioning scale read if it were used to
> weigh the object?
>
> c) If the object were allowed to fall, what would be its acceleration
> relative to the nearby planet?
>
> John Mallinckrodt      mailto:ajm@csupomona.edu
> Cal Poly Pomona          http://www.csupomona.edu/~ajm