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.