View unanswered posts | View active topics It is currently Sun Oct 22, 2017 12:27 am



Reply to topic  [ 7 posts ] 
Zero-G Starting & Stopping 
Author Message
Centennial Attendee
User avatar

Joined: Thu Apr 10, 2008 10:46 am
Posts: 532
Location: Aurora, IL, USA, Terra
Post Zero-G Starting & Stopping
Elsewhere on the Web, a friend posted:
Quote:
Well, I must have seen a sentence like this a million times in various
SF stories: "If you push on a rock in zero G, remember that you can't
stop it with a shove."

Another friend wrote:
Quote:
Really? I don't think I ever have. Can you give an example,
for context?

Sounds like Heinlein, to me. Can anyone recall in which story (or stories) a statement like this appears? Just now I can't.

(I'm reasonably certain Clarke treated similar ideas, but the diction rings my Heinlein bell.)

_________________
Bill Higgins
bill.higgins@gt.org
http://beamjockey.livejournal.com


Thu Sep 10, 2009 8:48 pm
Profile WWW
Heinlein Nexus
User avatar

Joined: Thu Apr 10, 2008 8:10 am
Posts: 2228
Location: Pacific NorthWest
Post Re: Zero-G Starting & Stopping
I'm not quite grokking the intent of the statement. What's the difference in impulse between a push and a shove?


Fri Sep 11, 2009 12:12 am
Profile WWW
User avatar

Joined: Tue Dec 02, 2008 6:24 am
Posts: 265
Location: Northwest Georgia
Post Re: Zero-G Starting & Stopping
I believe the quote is from The Rolling Stones when one of the twins were getting impatient about recovering their bikes that they had abandoned when they matched with the Wargod and suggested that they give them another pull. Actually, I never quite understood it myself why you couldn't stop it with a shove. It might have to do with the catcher not being able match the center of gravity to stop it without causing it to spin.

The ABC series Defying Gravity used the exact sequence a couple of episodes ago when the physicist shoved a large cargo packet at the Venus Lander pilot and amputated her finger. In this case, she didn't see it and didn't attempt to stop it as far as I could tell.


Fri Sep 11, 2009 3:23 am
Profile WWW
PITA Bred
User avatar

Joined: Wed Apr 09, 2008 12:17 pm
Posts: 2401
Location: The Quiet Earth
Post Re: Zero-G Starting & Stopping
In the case of the mass of bikes, the tugs would be additive. One tug = stop with more or less equal force. Two tugs = twice the force to stop it. Etc.

I could see where two or three hard tugs could create a momentum far harder to stop than the perpetrator might think. It's a case where the character is fooled by how the mass would behave if it were, say, a rolling cart on a planet surface. Newton's law, etc.

Pretty slick example, but it does require some thought and basic physics to unravel.

_________________
"Hier stehe ich. Ich kann nicht anders." - Luther
In the end, I found Heinlein is finite. Thus, finite analysis is needed.


Fri Sep 11, 2009 7:10 am
Profile
Heinlein Biographer

Joined: Thu Apr 10, 2008 1:33 pm
Posts: 1024
Post Re: Zero-G Starting & Stopping
I was going to bring up Defying Gravity, too -- what a weird show!


Fri Sep 11, 2009 8:03 am
Profile
Centennial Organizer
User avatar

Joined: Sun Apr 13, 2008 1:34 pm
Posts: 200
Post Re: Zero-G Starting & Stopping
Sounds like it's assumed that a shove would just angle the item in some other direction rather than stopping it.


Fri Sep 11, 2009 4:50 pm
Profile
Centennial Attendee
User avatar

Joined: Thu Apr 10, 2008 10:46 am
Posts: 532
Location: Aurora, IL, USA, Terra
Post Re: Zero-G Starting & Stopping
Update: Richard Rostrom in Chicago was able to come up with the passage the first guy was probably recalling. It's from chapter 9 of The Rolling Stones , "Assets Recoverable".

Rich writes, "The Stone family is retrieving some cargo previously set adrift..."

Quote:
"Easy now," his father cautioned. "We don't want
bunch of bikes in our lap. There - 'vast heaving.
She's started."

Castor became impatient and suggested that they give
the line another tug. His father shook his head.
Hazel added "I saw a green hand at the space station
try to hurry a load that way. Steel plate, it was."

"What happened?"

"He had started it with a pull, he thought he could
stop it with a shove. They had to amputate both legs
but they saved his life." Castor shut up.

_________________
Bill Higgins
bill.higgins@gt.org
http://beamjockey.livejournal.com


Fri Sep 11, 2009 10:14 pm
Profile WWW
Display posts from previous:  Sort by  
Reply to topic   [ 7 posts ] 

Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group.
Designed by STSoftware for PTF