Trajectory is the path a moving object follows through space. In physics class we'd create our own trajectory tests using a massive homemade sling shot – consisting of a bicycle helmet, stretchy surgical tubing and football field uprights. With a little bit of man power and your obligatory water balloon we'd fire our "objects" down the football field. Using the measurements on the field, each student was able to figure out the trajectory of their own water balloon.
Now, I'm not going to breakdown the formula for trajectory of a projectile because there are too many variables that I will inevitably screw up. Plus, if you're an engineer you should have an idea of some of the formula’s variations.
But if you want to work on figuring out trajectory in a vacuum, without having to do much pen to paper problem solving, try out The Discovery Channels NLOS Cannon Challenge. Part violent, part mathematic, it’ll occupy for a little while at least.