Re: Internal or external?

[Robert Carlson <Raacc@AOL.COM>]

Leigh,

To clarify your definition of weight in my mind, please tell me the weight in
the following cases.  I have a 100 kg mass with a density of 5000 kg/m^3.
The mass is placed on a bathroom scale in a tub that can be filled with
water.  The tub is placed in an elevator that may be accelerated and is at a
location where g is approximately 10 N/kg to simplify calculations.  What is
the weight of the mass in the following cases, first with no water in the
tub, and second, with enough water to completely submerge the mass?

1.  The elevator is at rest.

2.  The elevator accelerates up with a = 5 m/s/s.

3.  The elevator accelerates down with a = 5 m/s/s.

Thanks,

Bob Carlson



In a message dated 10/10/99 1:56:20 PM Central Daylight Time, palmer@SFU.CA
writes:

> The weight of an object is what is recorded on a scale supporting
>  the object when it is at rest. This operational definition can be
>  expanded to include moving objects. In that case the weight of the
>  object is the magnitude of the vector sum of the forces exerted on
>  it by the entities in contact with the object. This subsumes the
>  previous definition, of course, but it also accounts for the weight
>  of objects which are in accelerated frames, often called "apparent
>  weight" or "effective weight". I consider these latter "concepts" to
>  be gratuitous. They are unnecessary in my opinion, and they smack of
>  geocentrism as well!