Re: [Phys-l] Work and Energy: which first?

["Jeffrey Schnick" <JSchnick@Anselm.Edu>]

John Decker wrote:

> Here's how I define it:
>  http://www.av8n.com/physics/thermo-laws.htm#sec-energy

Thanks for sharing your clear definition of energy.  Your recursive
definition (the statements that a few different kinds of energy are
energy and that anything that can be converted into any of these or into
that which can be converted into any of these is energy) makes a lot of
sense but it does raise a question: For the systems you used to argue
that the capacity to do work definition is wrong (2 hot potatoes and a
heat engine vs. a hot potato, a cold potato, and a heat engine); how
would you convert the energy into one of the forms you listed
(translational kinetic energy of an object of mass m, gravitational
potential energy, spring energy, capacitive energy, and inductive
energy)?

Also, stating that energy is "anything that can be converted..." implies
that energy is "something" rather than a characteristic of something.

Finally, regarding the capacity to do work definition, a hot potato
alone has the capacity to do work.  To demonstrate how much work it has
the capacity to do, use it with an ideal heat engine and an ideal
thermal reservoir at 0 K.  You can use the latter two devices in a
thought experiment to show that a pair of hot potatoes has more energy
than that of a hot potato and a cold potato.

Jeff Schnick