Creating a catapult has shown me many things relating to physics. What we have learned in class that relates back to a catapult is projectile motion and projectile angles. When you use a catapult you can find its velocity, distance, acceleration and time. You are able to find its horizontal and verticle projectile. The horizontal velocity will be constant which means the acceleration will be 0 m/s^2. Its verticle component would have an initial velocity of 0 and its final velocity would increase. You can use the kinematic equations to solve for its velocity, distance, acceleration or time. You just have to know three of the five to find the unknown.