I just wanted to share this, because I was surprised at how difficult throwing something 100 mph (45 m/s) is, even with a sling.
I filmed myself slinging with my new Pocket Radar. The nice thing about this unit is that it will work with the projectile going toward it, or away from it. In this case, I set it up behind a baseball target and was slinging lacrosse balls. Slinging at a comfortable speed, I averaged roughly 75 mph (33.5 m/s). My best speed was (not in the video) 94 mph. I might be able to break 100 with a lacrosse ball, but I don't want to try in my backyard in fear of missing.
I wonder if a stone has a big enough cross-section for this thing to pick up... I think I could break 100 mph with a stone no problem.
https://youtu.be/M5MRHhEL3rM