Newton's three laws of motion are summarized as follows: Newton's first law states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force. Newton's second law states that the rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of the force. Newton's third law states that if body A exerts a force on body B, then body B simultaneously exerts a force equal in magnitude and opposite in direction on body A.