Law 1

  An object with no net force acting on it remains at rest or moves with constant velocity in a straight line

  Galileo speculated that if a perfectly smooth object were on a perfectly smooth horitzontal surface it might travel forever in a straight line. It was to Newton, however, to develope Galileo's idea more fully. If an object with no net force on it is moving at a constant speed in a straight line, it will continue to do so. If it is at rest, it will remain at rest.
  Objects often have more than one force acting on them, think of the rope used in a tug-of-war; the members of one team pull the rope one way, the people on the other team pull it in the opposite direction. If the two teams pull with equal strength, the rope will experience no net force, even though these are obviously forces acting on it. If one team pulls harder than the other, though, the rope will begin to accelerate.