Re: [Phys-l] Dynamic equilibrium in mechanics

[Rick Tarara <rtarara@saintmarys.edu>]

The importance probably lies in reinforcing (in student's minds) that 
equilibrium, zero acceleration and consequently zero net force, CAN exist in 
a dynamic realm.  Important because most students are firmly in the 
Aristotle camp when it comes to their instincts about motion and a big piece 
of that involves the idea that ALL MOTION requires a sustaining force. 
Moving from the natural state of motion is to BE AT REST to TO BE 
UNACCELERATED is the heart of Newton's first law but it is also a big 
stumbling block for most students.  Reinforcing the idea with the 
nomenclature of 'dynamic equilibrium' is maybe not a big help here, but is 
of some minor use.

Rick

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Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, IN
rtarara@saintmarys.edu
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----- Original Message ----- 
From: "Savinainen Antti" <antti.savinainen@kuopio.fi>
Subject: [Phys-l] Dynamic equilibrium in mechanics


> Hi,
>
> I have occasionally seen the term "dynamic equilibrium" describing 
> situations in which the object is moving at constant velocity and the net 
> force on the object remains zero. Furthermore, when object is at rest the 
> equilibrium is called "static". I'm not sure, however, that there is much 
> physical insight in this distinction since both cases include zero 
> acceleration. Zero velocity and constant velocity have equal footing: both 
> cases (zero net force, zero acceleration) imply an inertial frame of 
> reference.
>
> Any opinions whether the distinction (static vs. dynamic equilibrium) is 
> useful in teaching mechanics? (The idea of dynamic equilibrium is, of 
> course, useful in thermal physics and chemistry.)