Re: Energy before work" (was work done by friction)

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

A student in your class could ask:

1) How do I calculate that quantity (see below)?
2) Why should it be done with the formulas provided?
3) How do we know that what is stated in your last
    sentence is true?

Please answer these three questions. Assume they already
know how to measure some forces and accelerations.

paul o johnson wrote:

> Ludwik Kowalski wrote:
>
> > Is it possible, and desirable, to introduce the concept of energy
> > before the concept of work? Leigh goes one step further, if I
> > understand him correctly, and suggests the total elimination of the
> > concept of work.
> >
> > Traditionally, W=F*d, and energy, loosly speaking, is the "ability to
> > do work" or (even more loosly) it is
> > "the preserved work". Work is done on an ideal spring now and that
> > spring does the same amount of work later. How could energy be
> > introduced after the concept of work is eliminated?
>
> Ludwik
>
> Why not follow Feynman's lead: Energy is an abstract quantity that
> cannot be measured, only calculated. When a force is exerted on an
> object and the object is displaced, the value of this abstract quantity
> for the object increases.