Re: If NOT a reactionless drive, will it work?

From: vernonner3voltazim (vnemitz_at_pinn.net)
Date: 07/16/04

  • Next message: Bilge: "Re: There is no gap between philosophy and physics - is belief evil?" 
    Date: 15 Jul 2004 20:33:38 -0700

    ghytrfvbnmju7654@mail.com (Jim Black) wrote:
    > > vnemitz@pinn.net (vernonner3voltazim) wrote:
    > > For the sake of simplicity, let's assume that when
    > > Superman applies his Super force to the end of the
    > > battering ram, it takes exactly one whole second
    > > for that mechanical force, moving at the speed of
    > > sound inside the battering ram, to reach the far
    > > end.
    > > >
    > > > \ | | | | | |
    > > > \ | | | | | |
    > > > | \ | | | | |
    > > > | | \ | | | |
    > > > | | | \ | | |
    > > > | | | | \ | |
    > > > | | | | | \ |
    > > > | | | | | | \
    > > > | | | | | | \
    > > > | | | | | | \
    > > > | | | | | \ |
    > > > | | | | \ | |
    > > > | | | \ | | |
    > > > | | \ | | | |
    > > > | \ | | | | |
    > > > \ | | | | | |
    > > > \ | | | | | |
    > > > \ | | | | | |
    > > > | \ | | | | |
    > > > | | \ | | | |
    > > > | | | \ | | |
    > > > | | | | \ | |
    > > > | | | | | \ |
    > > > | | | | | | \
    > > > | | | | | | \
    > > > | | | | | | \
    > > > | | | | | \ |
    > > > | | | | \ | |
    > > > | | | \ | | |
    > > > | | \ | | | |
    > > > | \ | | | | |
    > > > \ | | | | | |
    > > >
    > > > |
    > > > |
    > > > |
    > > > V
    > > >
    > > > time
    > >
    > > Thanks! If I am interpreting your meaning, especially
    > > when comparing to a prior similar post by you, then
    > > last time you drew ordinary oscillations, and this
    > > time you have drawn incremental overall vibratory motion.
    > > While I can't say for sure what to expect until a
    > > test-gadget is built, I would not be surprised it the
    > > result was some sort of combination of the two drawings,
    > > a "two steps forward and one step back" sort of
    > > vibratory motion.
    > >
    > > Thanks again!
    >
    > What this is is a simplification of what would happen if
    > Superman gave it a whack on one end. In a more realistic
    > rod, the shock would eventually spread out over the entire
    > rod, as much of its energy gets converted into heat. The
    > other picture is the same thing, only this time, the
    > people all along the rod have exerted a force equal and
    > opposite to Superman's. In that case, there's a lot of
    > vibration, but the center of mass of the rod doesn't go
    > anywhere.

    OK, major misinterpretation on my part. But what I fail to
    see in your sketch above is the compressed region of the
    moving longitudinal wave -- the thing that takes one whole
    second to reach the far end of the battering ram. It LOOKS
    to me like you have all of it moving at once. Not possible!

    With respect to the center of mass, YES, if the battering
    ram could respond all-at-once to Superman's applied force,
    then ordinary oscillation would be the result (no overall
    permanent displacement of the center of mass). The response
    time that interferes with Superman's effort, however has the
    effect of NOT allowing the ram's center of mass to move as
    completely/easily as if the whole ram responded at once. That
    is, Superman's quick-struck compression of the end of the ram
    immediately constitutes SOME displacement of the center of
    mass, but not until that wave of compressed material reaches
    the far end of the ram, and the ram decompresses, can we say
    that the center of mass has any chance of moving as far as it
    would-have-moved-at-once, if whole-ram-could-have-moved-at-once.

    And whether or not it really DOES move as far remains to be
    proved! See, in the impossible situation of whole-ram-moving-
    at-once, after a strike from Superman, the simple equations
    F=m*a and v=a*t and d=a*t*t/2 apply to the motion of the ram.
    But in the real world, when the first whole second after that
    strike is being spent while the Force traverses the length of
    the battering ram, those equations cannot apply! The ram is
    instead experiencing "jerk", or rate-of-change-of-acceleration.
    It is NOT experiencing acceleration-as-a-whole, or velocity-as-
    a-whole, or even distance-as-a-whole. So, after that period of
    jerk has ended, HOW can any physicist say that the battering
    ram has moved as far as it would-have-moved, if it could-have-
    moved-at-once?
      
    MEANWHILE, the two thousand guys ARE moving the whole battering
    ram almost-at-once, every time they apply their distributed
    total Force in unison, toward Superman. The long-term result
    seems to me that the efforts of the men leads to more overall
    motion of the battering ram than the efforts of Superman.

    How would you draw that? Or, if there is an error in the
    preceding logic, what is the error?
    Thanks!

  • Next message: Bilge: "Re: There is no gap between philosophy and physics - is belief evil?"

    Relevant Pages

    • Re: If NOT a reactionless drive, will it work?
      ... and the battering ram will have finished experiencing ... > What happens is that the center of mass will start moving as the ... In the next moment, say T=0.05 second, the wave of compression ...
      (sci.physics)
    • Re: If NOT a reactionless drive, will it work?
      ... > Superman, and m is the total mass of the ram, this will ... final effect upon the battering ram as the 2000 men, ... In the next moment, say T=0.05 second, the wave of compression ...
      (sci.physics)
    • Re: If NOT a reactionless drive, will it work?
      ... > not misinterpreting it a third time, ... and the battering ram will have finished experiencing ... -> permanent displacement of the center of mass). ... What happens is that the center of mass will start moving as the ...
      (sci.physics)
    • Re: low-value
      ... See which is heavier, remembering mauve has more RAM. ... Do we have to go to Mass for salvation? ...
      (comp.lang.cobol)
    • Quantcast