Laws of motion and conservation of momentum

chapter 9 of book

Newtons first law of motion

states that every body will remain in a state of rest or travelling with a constant velocity unless an unbalanced external force acts on it

Newtons second law of motion

when an unbalanced force acts on a body the rate of change of the bodies momentum is directly proportional to the force and takes place in the direction of the force

Newtons third law of motion

states that if a body A exerts force on a body B then body B exerts an equal but opposite force on body A

principle of conservation of momentum

in any interaction between two or more bodies the total momentum of the bodies before the interaction is equal to the total momentum of the bodies after the interaction provided no external forces act on the system of bodies