[Phys-l] Physics versus math; was energy is well defined

[ludwik kowalski <kowalskil@mail.montclair.edu>]

On Feb 19, 2008, at 10:22 PM, LaMontagne, Bob wrote:

> Work is certainly a useful tool for introducing the kinetic energy.  
> The idea of starting with a single steady force acting on a point  
> mass producing simply and directly the quantity 1/2 m v^2 seems to  
> me to be a quick and easy way of justifying giving the most basic  
> energy (kinetic) that particular form. I feel much more comfortable  
> with that simple justification than simply pulling 1/2 m v^2 out of  
> a hat and defining it as KE. . . .

A pure mathematician can pull definitions out of a hat (in order to  
investigate consequences). But our definitions of new quantities (as  
introduced in textbooks, one after another) are not subjective. Why is  
the concept of work (a physical quantity expressed in joules) usually  
introduced before the concept of kinetic energy?  Because we think  
that this is pedagogically effective.

Ludwik Kowalski, a retired physisist
5 Horizon Road, apt.2702, Fort Lee, NJ, 07024, USA
Also an amateur journalist at http://csam.montclair.edu/~kowalski/cf/