How to Build a Supersonic Trebuchet
I don't know why, but this guy's explanation of the math he used to design this device had me laughing. I'm not quite sure what it was that got me going. It's not that the math is nonsense, it might be, but without sitting down and studying it I have no idea. I think it was his delivery, though I can't pick out anything in particular. Maybe because he was cramming so much into such a short exposition.
In any case, his machine is very cool. I don't like how it is powered by rubber bands, I would prefer a solid weight, but to get the required force (Force = mass x acceleration, that much math I do know) might require a weight of several hundred pounds, which would make it much less portable. Unless you could somehow use the weight of a vehicle to drive it. (Jack up the back end of your car, attached the puller cable, pull the pin and release the Kraken.)
The stated velocity of 400 meters per second is well above the speed of sound and is higher than the muzzle velocity of most handguns. One reason I like shooting the 7.62 x 25 cartridge is because it is supersonic and delivers a nice satisfying crack when fired.
Now he needs to work on accuracy.