Simplifying golf swing physics

Parametric acceleration is the inward pull just like you do when twirling an object on a string.  To make the object go faster you have to pull harder and faster on the string.  In a golf swing, the object (club head) and the string is the entire unit of the club shaft and lead arm which is attached at the shoulder.  The shoulder is the center of that circle not the spine.  I demonstrate this in a clipwww.youtube.com/cortsonlaw  The faster the left shoulder moves up the faster the club head travels.  Caveat; in doing so the club face will open dramatically so there must be a compensation in holding the club to account for this.  There are two circles in a swing.  The arm swing and the body turn.  The swing center for the body turn is the tail bone. Hogan told John Schlee (his only pupil) to get his tail bone over his left heel as fast as he could and then turn toward the target.

Conservation of angular momentum and a decrease moment or inertia come into play with the body motion adding to acceleration.  Simply put, conservation of angular momentum is what we see when an ice skater spins.  To spin faster the skater pulls her arms close to the body thereby increasing the speed of the spin.  In much the same way a golfer can use this by keeping his hands as close to his body as he can as he turns toward the target.  The closer the hands the faster the turn.  Decrease in the moment of inertia comes from shortening the radius.  A short pendulum moves faster than a long one.  To shorten the pendulum in a golf swing we bend the wrists backward creating what golfers term "lag".  This lag creates torque in the wrist.  The wrists snap out at the bottom of the swing without any effort being applied in the same manner as the bristles on a brush snap when the torque is released.  Trying to consciously apply pressure using your hands and arms to hit is tantamount to drawing an arrow back with a bow and the trying to push the arrow forward.  

I have an excellent demonstration of all this in the Pure Force Golf DVD.  www.pureforcegolf.com