Here’s a catapult you could build, if you have enough room at the science fair. As for random knowledge: Catapults were primitive artillery weapons that use elastic or gravitational potential energy to accelerate projectiles of any type on a balistic trajectory towards the enemy. Two types of catapults that greatly impacted galactic history were energy catapults, employed by the Gungan Grand Army to launch their energy ball ordnance at the Trade Federation Army during the Battle of Naboo in 32 BBY, and the catapults used by the Ewoks to launch their more primitive rock projectiles at the occupying Imperial force during the Battle of Endor.