Physics of a falling Slinky Spring: the motion of the TOP end is cool too!

There are already a number of videos focusing on the bottom end of a dropped slinky spring. In this video I show that there is really neat physics happening at the top end too.

Note about the graph (mentioned at 5:25) - notice how the end bit of this graph is a straight line as it then falls as one object in free fall. The cool part is how this line would go through the origin if you extrapolated back in time. This makes sense as the *average* acceleration must be that of "g" (and the fact that it was dropped from rest).

[ethanburnell]

This is actually unbelievable! Love the video!

[Observer]

It helps tp realize that this is a compression wave traveling downward. Focusing so much on the acceleration keeps you from realizing that after the initial acceleration, the downward speed is slowing.
As the spring shrinks, the restoring force decreases.
As the top recombines with the coils below, it is traveling faster, so the added mass of the lower coil slows the combination of mass. So, yes, the added mass of each new 'lower' link provides the upward reaction force which is a resistance to accelerating downward.

[Ozzy]

Great video, thanks for making and sharing!
Regarding the plot at 5:25 and your notes:
"
Note about the graph (mentioned at 5:25) - notice how the end bit of this graph is a straight line as it then falls as one object in free fall. The cool part is how this line would go through the origin if you extrapolated back in time. This makes sense as the average acceleration must be that of "g" (and the fact that it was dropped from rest)."
This does not seem correct and here is why I think this. The acceleration is on the springs CG, not the top of the spring. Thoughts?

[mohnishsingh]

Sir you are amazing love to physics from 🇮🇳

[bigsad]

I thought this was a hoax at first but it definitely makes sense!

[lfritz]

I am not an educated man but my intuition dose understand it I think your missing the two sides of the slinky hitting in a back and forth wave motion