Re: [Phys-l] workable versus unworkable energy

[JMGreen <jmgreen@sisna.com>]

Brian Whatcott   says the following:

> In the case of current interest: a car tire can expend an auto's
> kinetic energy in heating the tire and heating a patch of blacktop,
> and it can expend kinetic energy in shearing a surface layer of rubber.
> The energy consumed in the heating side effect is not accessible
>   for work use.

Brian, let me recast your msg in different terms:

Energy, what ever its definition, is not a substance,  a system's 
kinetic energy can not be "expended,"  Nor can energy be "consumed". 
Energy is a property of a system as is its color.  Maybe a string 
theorist will disagree.

A car can increase its property of kinetic energy by having work done 
on it.  We can call that energy "internal energy" of the gas and 
rubber if you will, and say that the tire has been "heated,"  but it 
will always be the case that that system can do work by placing it 
adjacent to a cooler system.

You might try to invent a system at T=0 of course.

Jim


J M Green
Email:  MailTo:JMGreen@sisna.com
WWW: HTTP://users.sisna.com/JMGreen