Abstract :This research proposes the change of damping�coefficient regarding minimum displacement. From the mass with�external forced and damper problem, when is the constant external�forced transmitted to the understructure in the difference angle�between 30 and 60 degrees. This force generates the vibration as�general known; however, the objective of this problem is to have
minimum displacement. As the angle is changed and the goal is the�same; therefore, the damper of the system must be varied while�keeping constant spring stiffness. The problem is solved by using�nonlinear programming and the suitable changing of the damping�coefficient is provided.