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Mark Wilson (mmwilson2@earthlink.net)
Tue, 7 Nov 2000 14:5:38 -0500
Hi;
There are a number of items on your page that are either somewhat incorrect
or unclear. For one, since the gravity is due to centripedal acceleration
(w*r^2, where w is the rotational velocity in radians/s), it drops off
exponentially, not logarithmically.
Secondly, "centrifugal force" is a layman's term which isn't used in
science. There is no such thing. Take a horizontally spinning carnival
ride. It spins up, you get squished to the outside of the seat. What you
are experiencing when spun is an acceleration, or centripedal acceleration.
Centripedal acceleration is the acceleration a body must have towards the
inside of a circle for it to stay on a circular path. Since you have mass
and inertia, your body resists the acceleration, causing you to press into
the outside of the seat.
If you jump up from a spinning colony cylinder, you are not "pushed down"
by the air. Since you are travelling at the same velocity as the cylinder
when you jump up and leave the colony surface, you are in essence flung
back down to the surface due to you velocity and acceleration. When you
jump on the colony, you appear to go up and down. But actually, you are
also traveling sideways due to the spin. Lets say you are standing along
the colony axis, facing along the axis. When you jump, if you jump up at 5
ft/s, you are still traveling sideways at the same speed as the colony
spin, and this combined velocity, part up, part sideways due to spin, is
what pushes you back into the colony. You simply re-collide--there is no
attraction involved.
So, if you jump, the colony also will not spin out from under you very
much--relatively speaking, you and it are travelling at the same speed. If
you jump straight up in a moving school bus, does it drive out from under
you? Nope. Same idea on the colony--relative velocity (except that the
rotational component of velocity does kick in a bit).
BTW, A colony cylinder that has a 500m radius ( a 1 km diameter) would need
to rotate as follows:
earth g = 9.81 m/s^2 = colony g =w*r^2
Solving for w, w= 9.81/(r^2) = 9.81/250000 = 3.924*10(-5) rad/s
In more common terms, to convert rad to degrees, multiply rad by 180/Pi.
Therefore, 3.924E-5 rad/s is 0.0022 degrees/s. or 0.1349 degrees per
minute. Or, 2668 minutes per revolution, or one turn every 44.5 hours.
Make the colony 250 m in diameter, and the rotation rate increases to:
w = 0.0002 rad/s = 0.009 deg/s = 0.5396 degs/min -> 667.2 minutes per
revolution, or 11.11 hours per revolution.
What about if you are at the axis of the colony, where the radius is zero,
and you are pushed towards the outer wall? Well, the only way you would
have motion is if something pushed you towards the wall. As you came
closer to the spinning wall, you would have NO attraction to the wall. If
there is an atmosphere, the air being dragged along with the cylinder wall
would create a wind relative to you, which you slowly speed you up in the
direction of the colony spin and pull you further out to the wall until you
schmacked into it. Depending on how much drag you have, the air can speed
you up tangentially a lot, causing you to smack nearly vertically into the
wall as if you fell from a height. If there were no air in the colony, you
would travel straight out to the wall, which to you would look like a huge
moving wall. Depending on the colony size, it could be moving quite fast.
Your impact would then be more like jumping out of a moving car than
dropping from a height.
Yeah, I have a couple degrees in this stuff--I'm not making it up.
To the previous message:
Being at the center of a mass does not crush you. At the center of the
earth, assuming there was no heat, you would be experiencing gravity from
all directions. Since the mass casing the gravitation would be around you,
you would be PULLED in all directions, making you essentially weightless.
The gravitational force ACTS through the center, but is not concentrated
there. If you travel to the center of a splinting object, you would feel
essentially no force. Try sitting on the edge and then the center of a
merry-go-round to see what I mean.
> [Original Message]
> From: Vince Leon <vleon@email.arizona.edu>
> To: gundam@aeug.org <gundam@aeug.org>
> Date: 11/7/00 11:06:43 AM
> Subject: RE: [gundam] Gravity within a colony (was: Funnels and flying MS)
>
> Okay folks, I had a brief discussion on this over a year ago with -Z-,
here
> it goes. Gravity inside a colony is created by centrifugal force as the
> colony spins. So the farther away you are from the center the more
gravity
> you will experience, which means it if you are at the center of the
> rotating colony you will experience zero gravity. That is why the dry
dock
> is located along the center line of the colony.
>
> On earth, gravity is a pulling effect, you are being pulled down; in a
> colony it is a pushing effect, you are being pushed "down". But if you
are
> not touching the surface will you escape the effect of the colony's
> "gravity", no. Because as the colony spins the atmosphere in the colony
> also begins to move at the same rate as the spinning colony and this is
> what will push you down.
>
> For more details on this you should look at -Z-'s web page 'The High
> Frontier'
> http://www.dyarstraights.com/msgundam/frontier.html
>
> --- --- --- --- --- --- --- --- --- --- --- ---
> Vince Leon
> vleon@u.arizona.edu
>
> -----Original Message-----
> From: KurenaiJiku [SMTP:kurenaijiku@rtsfan.com]
> Sent: Tuesday, November 07, 2000 2:06 AM
> To: gundam@aeug.org
> Subject: Re: [gundam] Gravity within a colony (was: Funnels and flying MS)
>
> I think you would have to be touching the colony. I think the same goes
> for planets as well...for example...the planets spin around the sun and
> planets spin on themselves. If you approached a planet in a ship at a
> certain trajectory, you would be able to orbit it due to it's
gravitational
> flow...so in fact, yes you would still experience gravitational force, but
> no where near if you were closer to the actual object that's spinning.
The
> gravity though is greatest at it's center as does apply to the Earth's
core
> (so technically no one can actually travel to the core otherwise they'd be
> crushed), and if you travelled to the center of the colony's cylindrical
> core, you would probably feel a substantianlly higher gravity force than
if
> you were outside the colony or on it's surface.
>
> Kuren
>
> >Given that gravity is simulated inside a space colony, would a totally
> detached
> >object (i.e. not touching the colony at all, and therefore not sharing
the
> same
> >spinning motion) within a colony still experience the gravitational force
> >brought about by the colony's longitudinal revolution?
> >
> >KurenaiJiku wrote:
> >
> >> F91 can fly in space or on Earth. Since space colonies simulate Earth
> >> gravity, and it flew on a colony and in space in the movie; yes it can.
> >> V-Gundam I'm pretty sure as it has the core block system, and like the
> >> RX-78, it can fly in space or on Earth without much configuration. But
> >> then again, the GP01fb and GP01 are both core block systems, with the
fb
> >> being the space version and the without being the Earth version. I'm
> sure
> >> any mobile suit can fly in any environment if it has verniers, it's
just
> >> that the main concern (as displayed in 0083), that the MS balancer
needs
> to
> >> be configured for space or Earth. It'd be weird to have a horizon
line
> on
> >> your gauge when in space, there really is no horizon. :)
> >
> >
> >-
> >Gundam Mailing List Archives are available at http://gundam.aeug.org/
> >
>
> -
> Gundam Mailing List Archives are available at http://gundam.aeug.org/
>
>
> -
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Mark Wilson
-
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