# The amazing floating suspended Slinky **URL:** \ **Category:** Factual Questions\ **Created:** [May 29, 2013, 7:02pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649 "2013-05-29T19:02:01Z")\ **Posts on this page:** 13\ **Page:** 2
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [May 30, 2013, 1:43pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/21 "2013-05-30T13:43:27Z")
> [@Leo\_Bloom](#): > > Why does it travel faster? Probably because the torsional spring constant is different from the one that controls tension/compression. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 30, 2013, 4:08pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/22 "2013-05-30T16:08:00Z")
> [@](#): > > Isn’t this effectively the same as the speed of sound in the slinky? 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. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [May 30, 2013, 4:37pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/23 "2013-05-30T16:37:03Z")
> [@Xema](#): > > Isn’t this effectively the same as the speed of sound in the slinky? > [@Chronos](#): > > 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. ---
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [May 30, 2013, 8:37pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/24 "2013-05-30T20:37:38Z")
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. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [May 30, 2013, 9:51pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/25 "2013-05-30T21:51:01Z")
> [@Mangetout](#): > > You could describe it as the speed of sound _in the medium of Slinky_ - but even that risks confusion. 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? ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [May 30, 2013, 10:27pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/26 "2013-05-30T22:27:32Z")
> [@Andy\_L](#): > > . . . initially, the contraction exactly cancels at the lower mass, while the upper mass moves faster than a free-falling object would. (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! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 30, 2013, 10:55pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/27 "2013-05-30T22:55:09Z")
> [@](#): > > Quoth **Xema** : > > 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? Yes, in the case of a solid steel rod, the relevant waves would unambiguously be sound waves. > [@](#): > > Quoth **KarlGauss** : > > (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, the cancellation is absolute, until such time as either the compression waves or the upper falling layers themselves (whichever comes first) reaches a point. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [May 30, 2013, 11:02pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/28 "2013-05-30T23:02:00Z")
> [@Floater](#): > > No it doesn’t. The speed of its fall increases with 32 feet per second every second. ??? Huh? You said exactly what I said! ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [May 30, 2013, 11:08pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/29 "2013-05-30T23:08:53Z")
> [@KarlGauss](#): > > (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! 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. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [May 30, 2013, 11:40pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/30 "2013-05-30T23:40:50Z")
Thanks **Andy** and **Chronos** ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [May 30, 2013, 11:54pm UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/31 "2013-05-30T23:54:00Z")
[A collection of lab assignments with Slinkys](http://freepdfdb.com/pdf/slinky-lab-report)from college physics teachers across the country. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [May 31, 2013, 12:07am UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/32 "2013-05-31T00:07:52Z")
> [@Leo\_Bloom](#): > > I’m reframing the phenomenon this way: say a metal plate is “supported,” more or less, by a stream of bullets from a gun below. Even after the shooting stops, there are still bullets en route, and until they run out the plate is supported, seemingly magically, even when the gun is off. By the way, this concept is very similar to the “Space fountain” [Space fountain - Wikipedia](http://en.wikipedia.org/wiki/Space_fountain) ---
**Author:** ![Sleel](https://avatars.discourse-cdn.com/v4/letter/s/73ab20/32.png) [@Sleel](https://boards.straightdope.com/u/Sleel)\ **Post date:** [June 1, 2013, 3:39am UTC](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649/33 "2013-06-01T03:39:04Z")
> [@Leo\_Bloom](#): > > I’m reframing the phenomenon this way: say a metal plate is “supported,” more or less, by a stream of bullets from a gun below. Even after the shooting stops, there are still bullets en route, and until they run out the plate is supported, seemingly magically, even when the gun is off. Congratulations, you’ve just reinvented the [space fountain](http://en.wikipedia.org/wiki/Space_fountain). [Previous page](https://boards.straightdope.com/t/the-amazing-floating-suspended-slinky/659649.md?page=1)