Aristotle was a Greek philosopher who lived from 384 BC to 322 BC. His work on physics, biology and ethics is still studied today. He is best known for his ideas about motion, which he divided into two classes: natural and violent.
Natural is the motion that occurs without the intervention of an outside force is called natural motion. Examples of this include falling objects, projectiles in projectile motion and objects moving toward their natural place (for example, water flows downhill). Aristotle believed that natural motion always occurs in a straight line at a constant speed unless some external force acts upon it.
Violent is the motion that occurs through an outside force acting on an object is called violent motion. Aristotle believed that violent motion does not occur naturally; it must be created by something outside the object being moved. For example, when you push a box across the floor, you are creating violent motion in the box because you are exerting force on it from outside yourself.
However, philosopher believed that all objects have a natural place in which they belong and that all objects have the potential for both types of motion. He also believed that no object can move itself from place to place unless there is something else affecting its movement (such as wind or another person).
