Re: Apparent weight

[Lowell Herr <herr@catseq.catlin.edu>]

Leigh,

Your first sentence from the paragraph below grabbed me.  Assume one has 
a 'frictionless' air table positioned on a lab table so the air table is 
horizontal or parallel to the surface of the earth.  If two pucks are pushed 
together and we photograph the 
interaction, momentum is conserved.  No problem thus far.  Now suppose we 
rotate the camera, positioned above the air table, at a constant speed.  
When we view the film, the pucks will appear to moved in curved paths due 
to the accelerating camera.  If I understand your first sentence, 
momentum will be conserved in the accelerated frame of reference.  I 
would have thought that momentum was not conserved.  Am I wrong or do I 
not fully understand what you mean by what I read below?  Would momentum 
be conserved for the colliding pucks in the accelerated frame of 
reference (due to the rotating camera) if I examined the movement of the 
pucks over a very short time period?  Thanks in advance for your answer 
and ideas.

Lowell Herr
The Catlin Gabel School

> You will find that conservation of momentum is a principle that works
> quite well in the horizontal plane in an accelerated frame. There is no
> need to give it up. I'm very curious about how you teach your students
> the first law of motion. I start by showing my students that we don't
> live in an inertial frame. The first law is not trivial by any means;
> it is a great intellectual feat to abstract to an environment one has
> never experienced for any appreciable time - and lived to tell of it!