Re: [Phys-L] defining energy

["John Clement" <clement@hal-pc.org>]

The idea of "many kinds" of energy tends to confuse students.  The concept
works much better if you get them to think of where you put the energy
rather than it being a different kind.  Along with this the notation should
always be E_location for the various places you put energy.  E_g, E_e,...
Once they have the concept of energy as just being moved from one place to
another, using conservation of energy is much more automatic.  But texts
still use KE rather than E_k, or PE rather than E_g.  And is thermal energy
really different?  It is just the kinetic energy of the molecules and/or the
potential energy when you stretch the bonds during a phase change.

Students at the high end of formal operational or who are at the theoretical
level should not have much difficulty, but since the majority of students in
an intro class are transitional with some thinking at the concrete
operational level, visualizing where energy goes is a vital process.  Make
the concept coherent rather than splintered into different types of energy.

John M. Clement
Houston, TX


> This is perhaps related to the fact that there is only one 
> kind of impulse but many kinds of energy inputs, and only one 
> kind of momentum but many kinds of energy.