🚀 go-pugleaf

I'm not sure this is a good analysis, in particular the claim that "it
(conservation  of momentum) cannot happen unless energy is also conserved".
 It seems to me that most collisions are cases where energy is not
conserved, but momentum is.  

In article <9407131320.AA50303@pen1.pen.k12.va.us>, James David Button
<jbutton@PEN.K12.VA.US> wrote:

> This may seem strange in reference to the question, but it may
> help in some ways.  I explain to my students that there are
> "Orders of Conservation Laws" with "Conservation of Energy"
> being the top one.  All others are subservient to it.  The
> analogy I use is that the US Constitution is the "top law" of
> the land, state constitutions are below it, county below it and
> so on down the line.
> Similarly, Conservation of Energy is the top law of physics (at
> least in the Newtonian world) and everything else
> conservation-wise is below it.
> Thus, it is easy to conserve momentum, but it cannot happen
> unless energy is also conserved.  This also gives some room to
> expand on both rotational and rectilinear motion and the
> conservation is those, particularly when a student has observed
> that a wheel that has rolled down a hill does not have the same
> rectilinear motion (energywise) at the bottom as it did
> gravitational potential at the top.  When the angular velocity
> is computed with the concommitant energies and momenta, the
> answer gets better.  Then we can get some idea of how
> comprehensive the conservation of energy law is.
> Hope this clears up a bit.  I know it is a strange way of
> putting it, but when you come from the state that authored the
> constitution and declaration, you get kind of philosophical
> about the whole ugly mess.
> --
> Dave Button -- Osbourn Park High School
> Manassas, VA 22111  There is no try, there is only do and not do.  Yoda

-- 
Joseph Bellina (jbellina@saintmarys.edu)