What is the definition of ballistics?

Ballistics is defined as the science that deals with the motion, behavior, and effects of projectiles. This definition encapsulates the entirety of the subject, which includes understanding how projectiles are launched, their trajectory through the air, and the impact they have upon reaching their target. This knowledge is vital for applications in various fields such as military, sports, and law enforcement, ensuring accuracy in aiming and predicting projectile behavior.

The other options focus on aspects that are related but do not encompass the full scope of ballistics. For instance, the study of chemical reactions in firearms pertains more to chemistry and does not address the physical motion of projectiles. The design of firearms involves engineering principles but is not the same as understanding projectile dynamics. Lastly, while the study of impact effects is relevant to ballistics, it is just one component of a broader field that also includes motion and behavior prior to impact. Thus, option B accurately conveys the comprehensive nature of ballistics as a scientific discipline.