Mangonel Catapults WORK just like third class levers (see picture to the right). The base of the catapult acts as the fulcrum which the catapult arm pivots on. In this case, the force is provided by tension in rubber bands which are attached to the crossbar of the catapult. When the arm is pulled back, the rubber bands tighten, so when the arm is released, the arm propels forward until it his the crossbar. The load acts as the projectile in the bucket. When the arm hits the crossbar, the projectile leaves the bucket and launches forward. This is due to Newtons first law which states that objects in motion want to stay in motion, likewise objects at rest want to stay at rest. The projectile is moving at the same spead as the arm and the bucket. When the arm and bucket stop, the projectile continues to move forward at the same velocity it was before. Gravity brings the projectile back to the ground which gives it its trajectory.report.