Back to the main page for the 21 metre (71 foot) long Slinky - including photos and two-channel piezo pickup sound recordings.
Back to the First Principles site for all sorts of fun-and-games, show-and-tell, DSP, etc.
Last update 14 April 2002. (Minor changes 2010-05-16.)
All files copyright Robin Whittle 2002. Please contact me
at rw@firstpr.com.au if you want to use them for any commercial purpose.
These videos were shot on a Sony TRV17E, transferred to computer and converted to Real Video 8 files, with a data rate of 512 kbits/sec, and resolution of 320 x 240 pixels - which is the maximum which seems to be possible. This seems to produce a better result than Video CD MPEG-1 352 x 288 pixels at 1,150 kbps (not counting the audio). These files can be played with Real Player which can be freely downloaded from http://www.real.com . Beware of them trying to sell you a full-featured version. You may have to ferret around to find the free version, but it is there, and its URL changes, so I won't give it here. In April 2002, the one to get is the "Free RealOne Player" - and you don't need to fill in the account information at install time in order for it to work.If you want to download these files to your computer and play them
from there, rather than repeatedly downloading them from my server,
hold your shift key down and click on the link. Then save it
to your hard drive and use Real Player (or another program for the MPEG-1 file) to play it from there.
Theresa gives Sliiiiiiiiiinky a good workout!
big-wiggle-1.rm 1.59 Megabytes 26 sec. Real Video.
big-wiggle-2.rm 2.47 Megabytes 42 sec. Real Video.
big-wiggle-2.mpg 16.62 Megabytes 42 sec. MPEG-1 3Mbps.
Please excuse my amateur camera work.
Standing waves occur when two waves of the same frequency are traversing a medium in opposite directions. The result is that some points in the medium become "nodes" and do not move at all, while the medium between these nodes does move a lot. The nodes are at half-wavelength spacings.
Here I am sending 1 Hertz horizontal waves, by trying to synchronise my hand movements to a watch's second hand. The waves lose energy as they travel, so near the camera, they are only about 1/3 the size. When these waves hit the end, which is being held still off-camera, they reflect back towards me. (They would reflect if the end was loose too.) Near the camera end, the reflected and non-reflected waves are about the same amplitude, so we see full standing wave patterns. Further towards me, the non-reflected waves are stronger and the reflected waves weaker, so the effect is diminished.
slinky-standing-waves.rm 2.04 Megabytes, 37 seconds, with sound.
Devil Fish assistant Ceri Hann is on camera and gives a brief discourse on how this phenomenon relates to Bootsy Collins' exit from the James Brown band.