| |
VK3ABK > INFO 23.07.02 07:58l 46 Lines 2241 Bytes #999 (0) @ WW
BID : 30890_VK3VSW
Read: DB0FHN GUEST
Subj: BALLOON FINALE
Path: DB0FHN<DB0ZWI<DB0HOT<OK0PBX<OK0PHK<OK0NAG<OK0PPL<RZ6HXA<SP7MGD<ON0BEL<
VK3TE<VK3SPB<VK3FRC<VK3VSW
Sent: 020723/0513Z @:VK3VSW.#WEV.VIC.AUS.OC #:30890 [Geelong] $:30890_VK3VSW
From: VK3ABK@VK3VSW.#WEV.VIC.AUS.OC
To : INFO@WW
Hello once again folks
This bulletin was compiled on 20/07/02 but was not sent to WW.
It seems that the balloon saga is set to run even further than I thought!
Ray, VK4LU has introduced Archimedes and Harry G0TEZ invokes Boyle's Law,
Avogardro's number and relative density of gases, (again!) Warren KB2VXA
reminds us of the apparent conflict between some aspects of Newtonian and
Einsteinian physics, but our 'frame of reference' is apart from this.
All important in their way, and except for the tale of Archimedes, I am
happy to let it be. I must thank Helmut DK2ZA for doing the research that
I decided against doing, early on, as too hard! I saw a more direct route
to the problem before going into properties of gasses. Gasp!
Archimedes has had more than his fair share of publicity, and he's even
been 'understood' by the media, who as a species need a handle to get a
hold on a scientific subject! But whether he ever fell into his tub and,
rudely awakend, 'floated' briskly to the surface and shouted the imortal
word, I am not prepared to say one way or the other!
But no doubt, my original question of specifically what causes a lighter
than air balloon to rise, can be 'explained' by referring to Archimedes.
It often is! However I asked you to consider the source of the force that
causes the balloon, airship, submarine, or even Archimedies unwashed bulk,
to rise in a surrounding medium.
If you consider that atmospheric pressure at sea level is 101 kPa, and at
say, 100 km, it is practically zero, then there is a pressure differential
of about 0.101 Pa m^-1 which acting on a balloon of, say, 0.5 m , would be
sufficient to move it upwards. Dimensions of an airship would provide more
force to lift the greater mass. Specifically, that pressure differential is
the source of the lifting force which then acts through the centre of mass.
Archimedes buoyancy, submarine operation and floating is a result of this.
I hope this doesn't sound too pedantic, but we have covered a lot of ground
in this discussion, and introduced a few red herrings!, but finally with the
help of Archimedes, and the many interesting bulletins, I am satisfied.
73. again. Dick. VK3ABK.
Read previous mail | Read next mail
| |
