Flexible structures undertaking impact while undergoing overall motion can be found in several industrial products these days. Transient motion and stress induced by impact should be considered elaborately to extend the life of the products. In the present study, a modeling method for a flexible beam with a tip mass that undertakes impact while undergoes large overall motion is presented. The tip mass takes the impact force and the transient responses of the beam are calculated by employing the assumed mode method. The stiffness variation caused by the large overall motion is considered in this modeling. The effects of the tip mass and the angular speed of the beam on the transient responses are investigated.