Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: CONSERVATION OF ENERGY



Hi John:

I find your distnction between "heating" and "warming" very useful.
Two different words ARE needed but warming is not necessarilly the best
term because most people would identify it with "less intense heating".
What about self-heating (as opposed to heating, which is impelled)?

I read Sherwood's paper again and noticed that he is indeed using the
term warming in the way you defined it. This escaped me when I read the
paper for the first time. I do not know how closely you followed this
thread. Do you remember these statements?

Let us examine the term "thermal energy". This term is not in my
dictionary, nor should it be in that of any physics teacher. It is
a source of confusion .... and a barrier to conceptual grasp.

It [m*c*dT] should properly be called heat, since a process, though not
a uniquely specified one, is implicit. It is certainly not an energy.

Bruce Sherwood (AJP, November 1984) would probably disagrees. On page 1002,
half way between the equations (4b) and (5), I see the following sentence.

The net work goes solely into increasing the thermal energy of the ...

I already accepted the idea that m*c*dT is heat. Is the above sentence
acceptable to you? I know you are away from home and you would probably
like to see the whole page before answering. I am using you as a generic
phys-L-er in this message.

More significant to me is his equation (5). It shows that the effective
distance (for the work done on a sliding object) is equal to one half
of the total sliding distance. Thus, if Bruce was asked to solve the
hypothetical student problem (posted yesterday) he would probably say that
the work done is mu*m*g*distance/2. Note that mu is the experimentally
determined coefficient of kinetic friction. I am puzzled. I wish more
people shared what they think a good student should be able to do after
learning some physics in an introductory course.

I hope you do not mind being "my generic phys-L-er". Why did I select you?
Because your message was the most recent in this thread, and because it
referred to the article of Sherwood and Bernard.

Enjoy your vacation. Do not spoil it by thinking about physics too much.
I am not going to Denver and will have my vacation in August.

Ludwik Kowalski