1. (Law of inertia): A body at rest remains at rest and a body in motion continues to move at a constant velocity unless acted upon by an external force.

2. A force F acting on a body gives it an acceleration a which is in the direction of the force and has magnitude inversely proportional to the mass m of the body: .

3. Whenever a body exerts a force on another body, the latter exerts a force of equal magnitude and opposite direction on the former. This is known as the weak law of action and reaction.

Law of Inertia, Newton's First Law, Newton's Second Law, Newton's Third Law, Newton's Law for Fluids, Strong Law of Action and Reaction, Weak Law of Action and Reaction