I'm just sharing a story from our old high school days. It's real, It happened... and it's sort of funny.
So basically they were working on thrust.... and used a long pipe to prove they could launch objects. It was interesting enough as he told me his teachers were highly interested in the outcome of the largest apparatus of the fair. However their school was on elevated ground and surrounded by a town and major highway. Seemed harmless enough. Upon execution the damn potato flew beyond view and everyone freaked right out because no one could spot the thing and now there's a projectile headed right towards the town. Shit was aimed away from the school (obviously) and right towards the town and highway. The potato was never found, but they disqualified the students because of just how dangerous they claimed it was. Bloody interesting fella too, if not a bit quirky.
My science teacher made a gas powered potato launcher once. We had these outside classrooms, small buildings with thin walls only used in the summer. He fired it in the direction of the classrooms in one of our lessons, thinking it wouldn't go that far. It ended up going through the classroom wall in the middle of a history lesson.