In this project we consider the motion of an object with mass m at the end of a horizontal spring on a level surface. By Hooke's law, when the spring is stretched (or compressed) by y units from its natural length, then it exerts a restoring force directly proportional to y: Restoring Force = ky, where k is a positive constant called the spring constant. Newtons second law of motion states that force equals mass times acceleration. Combining this with Hooke's law we get: my00 = ky ) my00 ky = 0