This is beyond cool.
David Eade (an engineer or engineering student, I don’t know) produced a video about trying to build a supersonic trebuchet. Eight minutes of it (1:00-9:00) are engineering equations that will make your head swim, but he demonstrates how to design (and what materials to use) and build his trebuchet.
The frame is wood, the elastic is rubber, and the arm is titanium. He calculates that the projectile is fired at over 400 metres per second. That’s 1440 kilometres per hour, which is faster than the speed of sound. You can actually hear the sonic boom in some of his test fires.
And sorry to harp, this also demonstrates how to make videos, very pleasant to watch and easy on the brain.