Trajectory Physics

Trajectories of two objects thrown at the same angle. The blue object doesn't experience any drag and moves along a parabola. The black object experiences drag.
In a physics context, a projectile is defined as an object propelled through space by the exertion of a force which ceases after launch. Using common physics, the trajectory of a projectile can be calculated.
The path of a projectile over a long distance (without the effects of wind resistance and drag) will trace a parabolic arc. With drag, the projectile will follow a similar arc, albeit, slightly asymmetrically and smaller (as can be seen in the diagram to the right).
Over a short distance, however, and when projected at a flat angle and high velocity (like from a gun), a projectile's arc is almost negligible. This can be of great use to forensic crime scene investigators, as crime scenes can be reconstructed, tracing the paths of bullets from their endpoints (identified from interactions with objects in the room) back to their points of origin.

Warlo, Tom A., Firearms, The law and forensic ballistics (2nd Ed.), CRC Press LLC, Florida, 2004
Young, Hugh D., Roger A. Freedman, University Physics (12th Ed.), Sears and Zernansky's, 2008
Image from Wikipedia. File is licensed under the Creative Commons Attribution ShareAlike 3.0 License.