Re: What perpetuates a 'slinky' to move from one step to the next lower one.

Hello,

You are right on both counts!  The slinky keeps moving down stairs both
because of the way it is wound *and* because (Potential) energy is stored 
in it.  In addition to this, it also continues to move because of momentum 
or inertia.  That's the short answer...

Like any object, if you carried it to the top of a staircase, you would be 
giving it potential energy.  If you then gave it a push and started it down 
the stairs, this potential energy would turn into kinetic energy causing 
the slinky (or any other object) to tumble down the stairs.  And by 
Newton's First Law, we know that once an object is in motion, it wants to 
stay in motion.

But in addition to this, the winding of the slinky determines how quickly 
it moves under the influence of gravity.  The physical motion of a slinky 
down a staircase is actually quite complicated: energy is transferred along 
the length of the slinky in a longitudinal or compressional wave, by 
transferring a pulse of energy from one molecule in the metal (or 
plastic) to the next molecule.  Therefore the speed of the slinky down the 
steps is dependent on how quickly the wave can move through the material of 
the toy, which is dependent on the spring constant and the mass of the 
metal (or plastic).

Besides the spring constant and the mass, other factors come into play, as 
well.  The length of the slinky and the diameter of the coils can effect 
the tumbling motion: One can easily visualize a slinky that's too short 
getting stuck after the first step or just rolling on its side down the 
staircase.  And we must also consider the the height of the step itself:  
Imagine (or try!) a shallow, wide step compared to a deeper, skinnier step. 

Hope that helps!
Amber