Re: [Phys-l] energy is well defined.

[John Denker <jsd@av8n.com>]

In the context of
  http://www.av8n.com/physics/energy-counterexample.htm

On 02/16/2008 06:51 AM, carmelo@pacific.net.sg wrote:

> How about heat or thermal energy generated when sands are continuously  
> falling at constant rate on a moving conveyor belt? 

Well, how about it?

> Electromagnetic  
> energy generated by friction to what extent measurable? 

What about it?

> Zero-point energy measurable?

Yes, it is measurable.  What's the point?

> Energy is *well* defined as "capacity to perform work" or "ability to  
> perform work"? 

No, that's not a good definition, for reasons explained in detail at
  http://www.av8n.com/physics/thermo-laws.htm#sec-workability

Note that the existence of a bad definition does not disprove
the existence of a good definition.

> It is, of course, better for the students to learn from something  
> concrete, then to abstract...

Maybe that's why Feynman started with an exceedingly concrete
example of conservation (Dennis and the blocks) before
abstracting away the concreteness.

Maybe that's why
  http://www.av8n.com/physics/thermo-laws.htm#sec-energy
also starts with a series of more-or-less concrete examples
before abstracting away the concreteness.

========================

Bottom line:  This brings us to a grand total of zero valid
counterexamples.