Probably because the torsional spring constant is different from the one that controls tension/compression.
One could describe it as a sound wave, but that could be misleading, as it could be confused with sound traveling in a heliacal path through the steel itself.
You could describe it as the speed of sound in the medium of Slinky - but even that risks confusion.
When I saw the video, I thought how Wiley Coyote runs off a cliff and never starts falling until he looks down and realizes he’s been running on air.
Right.
But I was thinking that if instead of a Slinky you used a steel rod, the time delay between top and bottom moving should correspond to the time it takes for sound to propagate along the length of the rod. Yes?
(emphasis added)
Is this actually the case, is the cancellation exact (with “exact” implying a real physical relationship) or is it just a coincidence because of the particular mass and length of spring used in this example? I think it’s a coincidence, but until you or another ‘physics type’ weighs in, I’m keeping an open mind.
Thanks!
Yes, in the case of a solid steel rod, the relevant waves would unambiguously be sound waves.
Yes, the cancellation is absolute, until such time as either the compression waves or the upper falling layers themselves (whichever comes first) reaches a point.
??? Huh? You said exactly what I said!
Like Chronos said, the cancellation is due to a real physical effect - I did the math for an arbitrary spring length, arbitrary mass, and arbitrary spring constant so there are no special numbers to be coincidental.
Thanks Andy and Chronos
A collection of lab assignments with Slinkysfrom college physics teachers across the country.
By the way, this concept is very similar to the “Space fountain” Space fountain - Wikipedia
Congratulations, you’ve just reinvented the space fountain.