Re: Questions for those who really know their physics . . .

Erik Max Francis wrote: 
Wildepad wrote:

Um, not quite. Why have so many good words been co-opted by science . . .
When the last loops of the Slinky are pulled from the upper step, they
are motivated to whip over the rest of the stack and begin the next
step. It is a combination of momentum and the potential energy stored
in the coils that causes that.
My concern is that when those loops are first free of the upper steps,
that portion of the coils which are extended just above the stack will
absorb much of that potential energy because they are being pushed up
and into the coils which are extended just below the moving end, which
is essentially floating free.

As has already been indicated, it doesn't make any difference at all what the mechanism is. If it works in an inertial frame, it'll work in any inertial frame. Stairs at rest or escalator steps moving with constant velocity both constitute inertial frames. If it works in one, it must work in the other. Physics does not distinguish between inertial frames; that's the relativity principle and the basis of special relativity.

What part of that do you not understand? 

  He already said; the physics.

You'd think (well, I'd think) that somebody would have looked in the horse's mouth, but a quick google shows no high-speed videos of a Slinky actually walking down stairs. A Dr. David Alciatore has many similar high-speed videos on his website:

http://www.engr.colostate.edu/~dga/high_speed_video/index.html

and has expressed (in private e-mail) interest in shooting and posting such a video, and maybe one on an escalator.


  Mark L. Fergerson

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