Newton's laws of motion are three physical laws that directly relate the forces acting on a body to the motion of the body. The first law states that every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. The second law states that the net force on an object is proportional to the time rate of change of its linear momentum ie. mass times acceleration. The third aw states that for every action there is an equal and opposite reaction.