A projectile is a body in free fall that is subject only to the forces of gravity (9.81ms‾²) and air resistance (Webster). It was Galileo who first accurately described projectile motion. He showed that it could be understood by analyzing the horizontal and vertical components separately. No one had done this prior to Galileo. People use to think that when something is shot in the air it goes in the air and some how hit something and explode, before Galileo which followed largely Aristotelian lines but incorporating a later theory of "impetus," which maintained that an object shot from a cannon, for example, followed a straight line until it "lost its impetus," at which point it fell abruptly to the ground. Later, simply by more careful observation, it was realized that projectiles actually follow a curved path. Yet no one knew what that path was, until Galileo. There was yet another brilliant insight that led Galileo to his most astounding conclusion about projectile motion. First of all, he reasoned that a projectile is not only influenced by one motion, but by two. The motion that acts vertically is the force of gravity, and this pulls an object towards the earth at 9.8 meters per second. But while gravity is pulling the object down, the projectile is also moving forward, horizontally at the same time. And this horizontal motion is uniform and constant according to Galileo's principle of inertia. He was indeed able to show that a projectile is controlled by two independent motions, and these work together to create a precise mathematical curve(Galileo). He actually found that the curve has an exact mathematical shape. A shape that the Greeks had already studied and called the parabola(Webster).Galileo reached was that the path of any projectile is a parabola.
For an object to be consider projectile it must be dropped from a height, thrown vertically upwards