A practice golf swing device which permits the swinger of a golf club to hit a variable height replica golf ball that is fixedly attached to a universally pivoting arm (swivel arm) that moves in direct proportion to the swing path and speed of the golf club. The motion thus initiated in the swivel arm may be measured at the base of the arm (knuckle ball) using an optical/digital sensing output as disclosed in U.S. Pat. Nos. 5,288,993 and 5,703,356 with this measurement being computed so as to numerically or graphically depict the movement. This graphical depiction may be viewed as a pictorial view of a golf ball in flight along the path that would be expected had the ball been struck by a golf ball with the same force and direction that is imparted to the replica golf ball, which is attached to the pivot arm of the device. The apparatus has a self-zeroing capability that provides an identical "at rest" position prior to impact. Thus, the only force that can affect the measured movement of the arm and the replica golf ball is the force applied directly to the ball at the point in time of impact.