Newton’s First Law or the law of inertia
: A body remains at rest, or in motion at a constant speed in a straight line, unless acted upon by a force.
Newton’s Second Law, or the fundamental law of dynamics
: When a force acts on an object, the object is set in motion, accelerates, decelerates, or changes its trajectory.
Newton’s Third Law, or the principle of action and reaction: For every action, there is an equal and opposite reaction: that is, the mutual actions of two bodies are always equal and directed in opposite directions.