# Projectile Motion

Aristotle (~400 BC) believed the rate at which an object falls was directly related to its mass. It wasn't until the late 1500s that Galileo questioned his ideas and accurately described projectile motion. His most relevant discovery was to divide motion into the separate components of constant forward velocity and the downward acceleration of free fall.

Objects fall to the ground at the same rate because the acceleration due to gravity is the same for all objects. All objects accelerate toward Earth at a rate of 9.8 meters per second per second (9.8 m/s/s) Horizontal motion of a projectile moves at a constant velocity, covering equal distances in equal time intervals. There is no horizontal acceleration. The vertical component of a projectile's velocity is subject to the force of gravity. It accelerates downward resulting in greater distances that are covered in each successive time interval. The horizontal and vertical components of projectiles are completely independent of each other.