=3D=3D>I take the scale with me in the shuttle and "stand" on it =
=3D=3D>and get zero. Therefore, I'm weightless.
I was very surprised by Leigh's statement (about 2 days ago =
see below), but I was too busy writing tests to reply earlier.
So now I'm left to reply "me too".
I'll be saying "I take the scale with me in the shuttle =
and "stand" on it and get zero. Therefore, I'm weightless."
again in my conceptual physics course in about 10 days. =
I think it is very clear because everyone has used a =
bathroom scale. Conversely they have never used a =
triple-beam balance (My lab equipment consists of a set =
of children's toys that I bring in from home - don't ask), =
do not know what one is or how it works. =
Sorry, but I felt a need to put in my $0.02. =
On to what Leigh wrote:
=3D=3D>Calling the shuttle a microgravity (better would be migro-gee) is
entirely
=3D=3D>appropriate. The gravitational field of the Earth varies by one pa=
rt in
a
=3D=3D>million over a radial distance of three meters from the center of =
the
=3D=3D>Earth if my quick mental calculation does not err*. That would be =
a
=3D=3D>microgee over a scale parameter appropriate to shuttle experiments=
=2E
=3D=3D>
=3D=3D>scratch misconception 5. Gravity in the shuttle is small, as one m=
ight
=3D=3D>well expect seeing those folks floating around in there. =
=3D=3D>
=3D=3D>* OK. Mental calculation redone below, partly to show the value of=
math
=3D=3D>in doing conceptual problems. Conventional symbols (g is grav. fie=
ld):
=3D=3D>
=3D=3D> G M
=3D=3D> g =3D -----
=3D=3D> 2
=3D=3D> r
=3D=3D>
=3D=3D>
=3D=3D> -6 dg dr
=3D=3D> 10 =3D ---- =3D -2 ---- ; r =3D 6600 km (or so)
=3D=3D> g r
=3D=3D>
=3D=3D>
=3D=3D> r dg
=3D=3D> dr =3D --- ---- =3D (-) 3.3 m
=3D=3D> 2 g
It appears that Leigh has proved that in the shuttle over =
a range of 3.3 meters dg/g varies by only a factor of =
1 ppm, so the term microgravity makes sense. But this
proof goes through just fine on the surface of the Earth
(with a reduction in the allowed distance to 3.2 m).
Either I'm missing something here or it was a joke.
Which is it? =