Re: ENERGY BEFORE Q

[Jim Green <JMGreen@SISNA.COM>]

>   Students already know how to add or subtract vectors but
>   not how to multiply them. Both Jim and JohnD seem to
>   agree that "work should be defined in terms of energy, not
>   the other way around." That what we should try to do.

Ludwik, I clearly have missed something -- but I here my name called again:

I don't know that either should be thought of as being defined in terms of
the other.

The concept of "energy" was a mathematical invention by Young before the
concept of work was derived. Energy was not discovered in the sense of an
"aha see this neat fluid". That folly came much later.

The concept of "energy" predates N#2 in its present form: F=ma

The concept of vectors comes much later.

But the integral  comes later as well:  Thus the work/energy principle is
derived as IntFdx==(work)=Int(ma)dx=Int(mdv/dt)dx=Intmvdv=(0.5mv^2==KE

I assume that we all know this cold.

Hence "energy" was not originally "defined" in terms of "work", but I don't
know that I would say that "work" is defined in terms of energy.  The
work/energy principle is derived.  But, yes, energy came first, but had the
form of mv^2, not 0.5mv^2

I feel silly posting this, but maybe a reminder is helpful.

Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen