Re: vector quantities and energy

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

Maybe another approach might be to consider how the quantities momentum and
energy are transferred from one object to another.  When momentum is
transferred through a collision, direction is very important.  A collision
that is entirely in the horizontal plane cannot produce any vertical
momentum--collisions on a pool table being an example (although then you
must discuss how and why sometimes you can have a ball jump off the table).
On the other hand, kinetic energy can be transferred into forms that clearly
have no direction (thermal energy for example).  In fact the thermal energy
in a room full of air depends on the kinetic energy of the molecules even
though the average _velocity_ of these molecules is zero.  This is a
somewhat less mathematical approach to the question.

Rick

***********************
Richard W. Tarara
Associate Professor of Physics
Department of Chemistry & Physics
Saint Mary's College
Notre Dame, IN 46556
rtarara@saintmarys.edu

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-----Original Message-----
From: GARY HEMMINGER <Hemmig@D-E.PVT.K12.NJ.US>
To: PHYS-L@LISTS.NAU.EDU <PHYS-L@LISTS.NAU.EDU>
Date: Thursday, January 21, 1999 9:32 AM
Subject: Re: vector quantities and energy


> Since we study momentum before energy I've had kids ask me the
> question - why isn't energy (particulary kinetic energy)  a vector?
> It strikes me that this is a great question because it can be
> addressed at so many levels.  Feynman would no doubt say something
> rather different to his colleagues than I would to my weakest 10th
> graders and so on.     How would you answer this?
>
> *****************************************
>  Gary Hemminger
>  Dwight-Engelwood School
>  315 E. Palisade Ave.
>  Englewood, New Jersey
>             07631
>  e-mail: hemmig@d-e.pvt.k12.nj.us
> ********************************************