Newton's Laws of Motion
Newton's First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force to change the motion. (The law is sometimes referred to as "The Law Inertia")
Newton's Second Law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object.
Newton's Third Law states that for every action, there is an equal and opposite reaction. (The law is sometimes referred to as "The Action-Reaction Law")