Re: Relativity

[jriley@lib.drury.edu (Jim Riley)]

Comments about Roger Haar's statements. 

1.  The entire wheel whether rotating or not is observed to be in the
reference frame of the observer.  Within that frame it may be stationary,
moving at constant velocity, or accelerating.

2.  Relativity does not demand that an observed object be not accelerating
only that the observer be making his/her observations in a non-accelerating
or inertial frame.   

If these statements were not true then we would be restricted to applying
the laws of mechanics solely to objects in the reference frame in which they
are at rest which would produce some pretty dull physics.

>  Hi,
>
> 	Concerning the relatisticly rotating and translating wheel:
> Two comments:
>
> 	1.  To the observer translating relative to the
> wheel, each part of the wheel is in a different reference frame.
>
> 	2.   Special relativity does not really apply to a 
> any part of the rim of a rotating wheel because each piece is
> accelerating, and NOT an inertial frame.
>
>
> 	But it is an interesting problem.  On first thought, 
> the path to the solution would seem to be to consider a non- rotating
> wheel next to the rotating one ( or a non-rotating groove containing the 
> rotating ring with a very small clearance).  Thus it would seem
> that the shapes of the rotating and non-rotating wheels must vary in the 
> same way.  BUT there is the problem of simultaneity,  like the problem of
> something longer than the barn in one frame being momentarily enclosed by
> the barn in another frame.
>
>
> Thanks
> roger haar U of AZ
Jim Riley, Department of Physics
Drury College
Springfield, MO 65802
e-mail: jriley@lib.drury.edu
Phone:  (407) 873 7233