The science of mechanics that deals with the flight, behaviour, and effects of projectiles are called ballistics. The word ballistics comes from the word ballista, which was a siege machine used for war during the late 18th century. Ballista was a weapon that is used to hurl boulders or spears against the enemy troops or walls. The boulder or spears used against the enemy was launched by the ballista, after which it would travel in a parabolic path and land among the enemy. The operators of the ballista have to be concerned about the angle to launch the projectile and the path they had to travel to gauge the landing position of the ballista. This is the reason the study of projectile motion is called ballistics. The path travelled by the projectile after it is launched is called the ballistic trajectory. The study of ballistics is important in modern warfare since it involves calculating the trajectories of modern warfare equipment like bullets, unguided bombs, rockets, and such other equipment. It also involves the designing of projectiles to attain desired acceleration and performance.