This should be easy (haha) to figure out... Just for fun, I took Barak's video and did a frame by frame analysis. Unfortunately, at 15 (low quality) frames per second you lose resolution right at the point where you need it at the release.
The plots for his throw show a smoothly accelerating swing over the last 6-7 revolutions, with substantial acceleration in the last 2. There aren't enough data points to predict the exact point of release.
Final radial speed works out to ~45 rad/s which assuming a 25" sling gives about 110kph. Arm/shoulder motion adds 9m/s in translation for a total speed of 150kph.
This isn't too bad actually! No aero-drag gives a range of >160m It doesn't look like this demonstration throw is taking full advantage of the "snap" though like I mentioned there isn't enough data in the last bit to be sure. I'd be comfortable accepting that the instantaneous radial speed at the time of release was as much as 50% higher. Maybe Barak can vet some of this...
Interesting thing to note are that Barak's hand moves only vertically during the spin up phase, and only through about 8".
I think I might write up a little prog (Sling analyser v0.1
) when I get some spare time. If there is interest I'll try to post an article. If we filmed a couple of throws with the intent of crunching the video we should be able to produce some intersting results - I can probably borrow a high speed camera later this summer.
Matthias