# Article in "The physics teacher" "Only two forms of energy"

1. Sep 13, 2016

### ZeroGravity

Hi
I remember reading an article some years back (5?) on a description of energy categorized into either potential or kinetic energy.
I think it was an article in "The physics teacher" but cant find it...
Anyone remember it?
Martin

2. Sep 13, 2016

### kuruman

The Physics Teacher 45, 88 (2007).

3. Sep 13, 2016

### ZeroGravity

4. Sep 17, 2016

### fog37

Hi,
Thanks for the article details. I will read it today.

Just to get the conversation started on this interesting topic, this is what I believe so far:

Fundamentally, those are the two types of energy (kinetic and potential). All other energies can be relate to these two.
A system is an entity composed of many parts which can have relative motion to each other (i.e. hence kinetic energy of the system is the sum of the part's kinetic energy).
The potential energy of a system is energy due to configuration, i.e. the mutual, relative position of the various parts to each other. Energy is a scalar quantity that expresses the ability of a system to cause changes in its own configuration. Work, another concept, is the mechanism through which the system can change its energy or the energy of another system...
One object can be the system or multiple objects can represent the system. We can define the system to include whatever we decide. For instance, if the system is composed of two distinct macroscopic objects but each object is formed by many sub-components...

Any correction or comment?

Thanks,
fog37

5. Sep 17, 2016

### robphy

6. Sep 17, 2016

### kuruman

I am not sure how the rest mass energy of an electron or the energy of a photon can fit this scheme.

7. Sep 18, 2016

### maline

Well photon energy can reasonably be called "kinetic" because it is frame-dependent- so it has to do with "quantity of motion". Electron energy can sort of be call "potential energy" because it comes from a non-minimal configuration of the Higgs field. But yeah, it's not a very elegant way of looking at things.

8. Oct 12, 2016

### Kajal Sengupta

I thought that Kinetic and Potential energy are the only two forms of mechanical energy. It is different from heat or light , for that matter any other forms of energy we know. Am I right? Your thoughts?

9. Oct 12, 2016

### Dr. Courtney

There are different approaches to categorizing and defining things. I try not to get dogmatic about the "right" and "wrong" approaches to these things.

Teaching overly simplified constructs is not really the best plan. When there are nuances and details that will become clear later as a student grows and matures and becomes exposed to the broader world of physics, I try and at least hint at it and communicate that the intro class is simplifying things that should not be taken as absolutes, but as useful definitions and categorizations.

In science, the question is almost never "Is it true?" but rather "Is it useful?"