Identifying the equations needed calculate force needed to launch projectiles the correct distance. This included identifying how each physical input variable (such as projectile weight) effected the launching process. All variables needed to be included in a unifying equation which decided how far we would pull the catapult's arm down. 
 

Collecting testing data to create graphs which correlated the catapult's arm position to distance projectiles were launched. This data formed the basis for our model making process.
 

Creating a reactive model which updated when a new projectile weight was inserted, this was done using Microsoft Excel. When inserting a projectile weight and desired distance, our model would output the angle we needed to pull the catapult's arm down to.
 

In addition to this, our model also calculated the force needed to fire a projectile, the corresponding spring extension on the design and then the drawback distance required for the arm.