My kid and I built a trebuchet years ago. If you are unfamiliar with that word, two things. One, I feel sorry for you. Two, a catapult directly launches a projectile.
A trebuchet uses a rope or cable to slingshot around the fulcrum arm to amplify distance.
Our first test run was in a large field. With a cantaloupe we cleared the fence and put it in some guy's back yard.

We took it to many a Boy Scout event. The launch weight was supplied by Boy Scout bodies standing on a platform. Much easier than transporting all that weight!