This is a perfect demonstration of where to look for Physics. Anywhere!
A simple question of “What if…” has led to a ‘front page’ article in the American Journal of Physics. I love it.
This is great for introducing the idea of cognitive dissonance. A student in a lecture or classroom will have misconceptions, show them this and that will flip their head around so that those misconceptions can no longer exist in their brains.
We can go further than this. After proving that all masses fall to the ground at the same acceleration, (think Galileo) demonstrating that it’s not like that in all cases by dropping a mass next to a slinky shows it’s not as simple as that. They’ll hit the ground at different times.*
What really gets me about this is that it holds true even if your drop a 10 foot pole. The top falls while the bottom of the pole waits for the information to get there before it moves. It just happens a lot fastest with a pole that a slinky.
*providing you are not dropping the mass from the same height as the centre of mass of the slinky.