The question is based on an incorrect understanding of Newton's laws. They are applicable in both examples - at least in their simplified models.
Individuals firing missiles will use Projectile Motion equations to determine where the missile will hit, so they can fire them with the correct trajectory at the intended target. An i-phone game, Angry Birds, uses projectile motion as well.
hypothesis on projectile motion
Because a projectile by definition, is in motion.
Projectile motion has two components horizontal motion and vertical motion. Gravity affects only the vertical motion of projectile motion.
The term ballistic refers to the trajectory or path taken by a projectile. Normally it refers to that part of a projectiles flight that is unpowered and unguided except by the forces of gravity and (if applicable) air resistance.
motion of a projectile
gravity
Gravity
A feather falling in a vacuum is not considered as a projectile motion. Gravity, which is absent in a vacuum, is one of the components of projectile motion.
Gravity
Gravity
No, gravity is only one of the vectors in projectile motion.