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Re: [Phys-L] friction



I think you’re oversimplifying history and making it sound like previous generations of scientists were too stupid to notice any of these issues. I’ll grant that they were trying to sort out ideas of energy and thermodynamics and forces et al and that did lead to confusions.

Nevertheless, I don’t think it “works” well to present Fdx in an introductory physics course as a purely “calculational tool” with no connection to concepts such as kinetic energy. That might be fine in an introductory calculus course (and even that is probably debatable) but I think in physics we want to present big conceptual frameworks such as conservation laws rather than mere computational tools, however rich they may be.

Just a thought, Carl

On Sep 26, 2017, at 11:07 AM, Bob Sciamanda via Phys-l <phys-l@mail.phys-l.org> wrote:

In Newtonian Force Dynamics F(dot)dr concerns ANY force and defines a numerical quantity which enables a rich calculational tool (http://sciamanda.com/Sans%20Work.pdf) for analyzing a myriad of situations (oscillators, Kepler orbits, etc) Here Fdx implies NO ( and doesn't even know of) transfer of "energy". Centuries later Fdx was defined to represent the transfer of a proposed conserved "energy" . Here, F is defined as that which makes this analysis valid - it does not apply blindly to ALL forces in All situations. Confusion has resulted by conflating these two completely different uses of the symbolism Fdx under the common name "WORK".

Bob Sciamanda
Physics, Edinboro Univ of PA (Em)
treborsciamanda@gmail.com
www.sciamanda.com

-----Original Message----- From: Anthony Lapinski
Sent: Monday, September 25, 2017 3:31 PM
To: Phys
Subject: [Phys-L] friction

Kinetic friction does negative work on a sliding book, which makes it stop.
And static friction moves us forward when we walk. But there is no
slipping, so static friction does no work on us. Yet we move forward. How
can this be explained to kids in terms of work and energy?

--


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Carl E. Mungan, Professor of Physics 410-293-6680 (O) -3729 (F)
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