In a message dated 24/01/2007, Brett3mr@............. writes:

Let me  borrow Einstein's thought-experiment box, the one with 
no windows that is  big enough to let me get inside. Sitting in the box, I 
coat the  bottom with thought-experiment ice, the kind that has no 
friction. Then I  set a 1Kg brass weight on the ice in the center of the 
floor and wait for  the thought-experiment earthquake to occur, which 
happens right on  time. Being that the quake is conveniently close, I 
observe that the  mass appears to be moving, which I record with my video 
camera. The  question is, what am I observing when I plot the motion of the  
weight? And then, can I tell anything about the nature of the motion  of 
the box (i.e. ground velocity or acceleration) from analyzing the  weight's 
apparent motion inside the box? Also, I observe that, since  there can be 
no (horizontal) force acting on the weight because of the  ice, it will be 
seeing no (horizontal) acceleration at  all.



Hi Brett,
 
    You are recording both the position and the time of  relative movements 
of the mass. From this you can infer the lateral acceleration  and velocity of 
the frame of reference, if you know that the mass is not  being accelerated.
 
    Regards,
 
    Chris Chapman






In a message dated 24/01/2007, Brett3mr@............. writes:
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  borrow Einstein's thought-experiment box, the one with 
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  big enough to let me get inside. Sitting in the box, I 
coat the=20
  bottom with thought-experiment ice, the kind that has no 
friction. The=
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  set a 1Kg brass weight on the ice in the center of the 
floor and wait=20=
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  the thought-experiment earthquake to occur, which 
happens right on=20
  time. Being that the quake is conveniently close, I 
observe that=20=
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  mass appears to be moving, which I record with my video 
camera. The=20
  question is, what am I observing when I plot the motion of the=20
  
weight? And then, can I tell anything about the nature of the mot=
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  of 
the box (i.e. ground velocity or acceleration) from analyzing the=20
  weight's 
apparent motion inside the box? Also, I observe that, si=
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no (horizontal) force acting on the weight because of the=
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  ice, it will be 
seeing no (horizontal) acceleration at=20
all.


Hi Brett,
 
    You are recording both the position and the tim=
e of=20
relative movements of the mass. From this you can infer the lateral accelera=
tion=20
and velocity of the frame of reference, if you know that the mass is no=
t=20
being accelerated.
 
    Regards,
 
    Chris Chapman