[Phys-L] Re: Energy is primary and fundamental? (was RE: First Day Activities or Demos)

[betwys1 at SBCGLOBAL.NET (Brian Whatcott)]

At 07:11 PM 8/11/2005, you wrote:
> As a counter to all the things you can deal with using energy:
>
> I am standing still on a level floor.  How do I start walking?  Answer that
> VERY BASIC question with energy please?
>
> Rick
>
> ***************************************************
> R.W.Tarara
> Professor of Physics
> Saint Mary's College
> Notre Dame, Indiana
> Free Physics Instructional Software
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Here I am - a dynamically stabilized bipedal servo
  (such is the unwanted complexity of the chosen example).
I relax the forward end of the bipedal terminals, and the
bipod rotates forwards, reducing its potential energy in
  exchange for rotational energy.
At an instinctively learned moment, I swing one bipod forward,
  folding it so as to clear the reduced clearance now available,
  and plant it one step forwards, straightening it dynamically
as it touches down.
The rotating mass of the thorax/abdomen now begins returning
  rotational energy to potential, but there is a loss of course.
This is made good by the parting movement of the rear foot
terminal.
  ...and so on.
Is there a problem?

Well, yes, of course there is a problem.  Physics teachers
  would do well to avoid intricate servo mechanisms of this kind.
They are not necessarily amenable to the wonderfully simplifying
  assumptions which are the glory of physical analysis.



Brian Whatcott    Altus OK    Eureka!