Re: [Phys-l] Mass and Energy

["Fayngold, Moses" <fayngold@ADM.NJIT.EDU>]

John Denker wrote:

> "Fayngold, Moses wrote:

>   No matter what you choose, if potential energy is a form of energy, 
> it will always be in the same units as energy. If you choose Gees 
> (it sounds good to me) then both - potential energy and total energy -
> will be in Gees. No matter how hard you try you will not find a system
> of units in which energy will be in Gees but potential energy will be in
> Boos.
   Oh really?  Who are you to tell me what I can and cannot choose
as my units of measure?
   Suppose there is a gauge that indicates altitude in feet, from
which I infer the gravitational potential energy per unit mass.
Also suppose there is a gauge that indicates speed in knots,
from which I infer the kinetic energy per unit mass.  In this
case, the conversion factor from kinetic to potential, in my
chosen units, is:
       9 feet per knot, per hundred knots
It is not unity.
   Are you trying to tell me that no such gauges exist?"

     Now I see yourself doing precisely what you were telling me
NOT to do in your previos message; but at the very end you DO 
excpress both terms in ONE system, which was precisely my point. 
BUT IN UOUR "COUNTEREXAMPLE" YOU FORGOT TO INCLUDE THE LAST TERM
IN THE EQ. (1) (which follows unavoidably from the Halliday-Resnik 
statement). In this case you will get the net energy on the left 
and the first two terms on the right in Gees, while the last term 
in Boos, or, if you choose CI, the former terms in Joules while the 
latter one in kg (WITHOUT c2!). 
   That's all.  

>  "In contrast, we know at least one system of units in which mass, 
> while being nothing more than a "form of energy", is in units other than energy.
  Again:  Who are you to tell me what I can and cannot choose as my
units of measure?  Maybe you want to measure energy and mass in
different units;  maybe I want to measure them in the same units
upon occasion."

   Maybe I want to be in two places at once or to be invisible; the nature
as I know it today does not allow me to do that.
 You are free to use any units. But in the end, within one equation, you express them ALL in terms of ONE common system.
 I am sorry to repeat banalities, but you have provoked me to do this. 
  
Moses Fayngold,
NJIT