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Re: CONSERVATION OF ENERGY



Looking for a precedent for the "energy before work" way of teaching
elementary physics I found an intersting reference. It is a textbook
ENERGY AN INTRODUCTION TO PHYSICS BY R.H. ROMER; many of you know that
the author is the editor of AJP. He introduces kinetic and gravitational
forms of energy (operationally as m*v^2/2 and mgh) before the concept of
work. This is done in connection with the study of a pendulum. The author
wants students to discover that the sum of two quantities is conserved.

This approach can be implemented in at least two ways, depending on
the equipment available. One is to use a camcorder, another to use a
camera and a stroboscopic source of light. The goal is to collect data
on how the velocity, v, and the elevation, h, are related. You can also
collect data on free fall, for example, with a motion detector. Ask
students to plot v^2 versus h and discuss the significance of the the
straight line. What is the unit of the quantity represented by the
negative slope? Why is the slope so close to 19.6 (2*g)?

I will try this approach in the Fall. Ludwik Kowalski