Ballistics

Ballistics (gr. βάλλειν ('ba'llein'), "throw") is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.

A ballistic body is a body which is free to move, behave, and be modified in appearance, contour, or texture by ambient conditions, substances, or forces, as by the pressure of gases in a gun or propulsive nozzle, by rifling in a barrel, by gravity, by temperature, or by air particles.

A ballistic missile is a missile only guided during the relatively brief initial powered phase of flight, whose trajectory is subsequently governed by the laws of classical mechanics, in contrast (for example) to a cruise missile which is aerodynamically guided in powered flight.

History
The earliest known ballistic projectiles were stones and spears, and the boomerang in Australia

Subfields
Ballistics is the work of projectiles from the beginning of acceleration to the time of impact with any target. Ballistics is often broken down into the following four categories, which contain detailed information on each category:
 * Internal ballistics (sometimes called interior ballistics): the study of the processes originally accelerating the projectile, for example the passage of a bullet through the barrel of a rifle.
 * Transition ballistics (sometimes called intermediate ballistics): the study of the projectile's behavior when it leaves the barrel and the pressure behind the projectile is equalized.
 * External ballistics (sometimes called exterior ballistics): the study of the passage of the projectile through a medium, most commonly the air between firing tool and target.
 * Terminal ballistics: the study of the interaction of a projectile with its target, whether that be flesh (for a hunting bullet), steel (for an anti-tank round), or even furnace slag (for an industrial slag disruptor).

Forensic ballistics
Forensic ballistics involves analysis of bullets and bullet impacts to determine information of use to a court or other part of a legal system. Separately from ballistics information, firearm and tool mark examinations ("ballistic fingerprinting") involve analysing firearm, ammunition, and tool mark evidence in order to establish whether a certain firearm or tool was used in the commission of a crime.

Ballistics research
Ballistics can be studied using high-speed photography or high-speed cameras.

Astrodynamics
Astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft. The motion of these objects is usually calculated from Newton's laws of motion and Newton's law of universal gravitation. It is a core discipline within space mission design and control.