Acceleration vs. Gravity

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3 total messages Started by wasser Mon, 27 Oct 1986 14:25

#7448

Author: wasser
Date: Mon, 27 Oct 1986 14:25

30 lines
1746 bytes

>  o  Given the old "accellerating-elevator-in-space" experiment,
>     how can one within the elevator tell the whether he is
>     accelerating or under the influence of gravity?

	Two ways to tell if your elevator is just sitting on a big mass:

	1) The acceleration is stronger at the bottom of the
	elevator because the bottom is closer to the center of
	gravity.

	2) Two plumb lines will converge slightly because both strings 
	point toward the center	of gravity of the mass.  The strings
	would hang parallel under acceleration in space.
 
	Warning: Experiment 2 can probably be fooled by appropriately
	shaping the large mass.
 
			-John A. Wasser
Work address:
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          ihnp4,imagen,ios,logitec,microsoft,mordor,nsc,purdue,pyramid,
          qubix,sci,sequent,Shasta,sun,turtlevax,ucbvax}!
	 decwrl!dec-rhea!dec-{viking,rainbo,mosiac,colors}!wasser
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P.S.  Design of experiments to test for properties 1 and 2 are left as
	an exercise for the reader!

Re: Acceleration vs. Gravity

#7452

Author: Guy M. Smith
Date: Tue, 28 Oct 1986 18:54

18 lines
1395 bytes

In article <6108@decwrl.DEC.COM>, wasser@mosaic.dec.com.UUCP writes:
> 
> 	1) The acceleration is stronger at the bottom of the
> 	elevator because the bottom is closer to the center of
> 	gravity.
> 
> 	2) Two plumb lines will converge slightly because both strings 
> 	point toward the center	of gravity of the mass.  The strings
> 	would hang parallel under acceleration in space.
>  
> 	Warning: Experiment 2 can probably be fooled by appropriately
> 	shaping the large mass.
Actually, Experiment 1 can also probably be gimmicked. The gravitational
acceleration within the earth doesn't change much until you get to the
core-mantle boundary. This basically occurs because the core is much denser
than the mantle so that the fact that you have less mass under you as
you go down is compensated by the fact that you are closer to the dense
core.

Re: Re: Acceleration vs. Gravity

#7466

Author: Derek J. Godfrey
Date: Fri, 31 Oct 1986 16:14

14 lines
1288 bytes

> In article <6108@decwrl.DEC.COM>, wasser@mosaic.dec.com.UUCP writes:
> > 
> > 	1) The acceleration is stronger at the bottom of the
> > 	elevator because the bottom is closer to the center of
> > 	gravity.
> Actually, Experiment 1 can also probably be gimmicked. The gravitational
> acceleration within the earth doesn't change much until you get to the
> core-mantle boundary. This basically occurs because the core is much denser
> than the mantle so that the fact that you have less mass under you as
> you go down is compensated by the fact that you are closer to the dense
> core.

I always understood gravity varied with r^2 between two bodies two non-
coincident bodies but r when one is contained within the other.

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