Category Archives: impact

What Happens at Impact

Because of a flexible shaft and a heavy clubhead, both flung at a stationary ball at high speed, impact in golf does not lend itself to a simple description.

From the top of the backswing to impact about 1/5 of a second elapses. The accelerating, clubhead builds up a considerable amount of speed. It meets the ball with a force of almost 2,000 pounds and remains in contact with it for 0.0005 seconds. During that time, the clubhead travels from 3/4” to 1”.

The force of impact with a stationary object, the golf ball, immediately slows the clubhead down by about 25 percent.

Spin gets applied to the ball, about 3-4,000 RPM with a driver, and about four times that with a 9-iron.

The heavier clubhead was in front of the shaft near impact, giving the shaft a concave shape in relation to the target. The collision of the clubhead and the ball slows the clubhead down more than the shaft, so the shaft flips into a convex shape in relation to the target.

Centrifugal force built up at impact pulls on the player’s hands with a force of about 40 to 60 pounds.

The golfer feels the shock of impact, but not simultaneously with the event itself. The vibration takes 0.00067 seconds to travel up the shaft to the player’s hands. By this time the ball has already left the clubface. From there the nerve impulse takes 0.01 seconds to travel to the player’s brain, by which time the ball has separated from the clubhead by almost 12 inches. Were the player to react in some way to the feel of impact, by the time a correction could be applied, the ball would be almost fifteen yards down range.


The Sound of Impact in Golf

You can tell a lot about your swing by watching ball flight. One famous teacher, John Jacobs, doesn’t watch anything else. That’s all he needs to see to make his corrections.

You can also tell a lot about your swing by the way impact sounds. Here is where hitting off a mat is truly an advantage. When you’re hitting the ball first and the ground second, you hear a click mushed up against a thunk — like a sharp thunk — and the ball shoots into the sky.

If you hit a little fat, you hear the thunk but no click. Too thin, and you hear the click, but no thunk.

In fact, when you hit off a mat, you should be using the sound of impact as a reality check. You can hit a little bit behind the ball on a mat and still get a decent result because the club will slide along the mat for a ways. Off turf, the ball wouldn’t go anywhere.

Putting is the same way. There’s a sound that only comes when you hit the ball on the sweet spot. That sound accompanies a strike that doesn’t resonate into your hands and you see the ball jump off the face of the club. Paul Runyan used to practice putting by ear.

Chipping? Same thing as swinging. There’s a click right on top of a thunk and the ball leaps off the clubface.

It’s easiest to get this sound with your wedges, harder as you got to longer clubs, but practice with one club until you can make this sound consistently with it before moving on to the next one.

Play by ear. The ball can still go right or left, but if you’re hearing the right contact, you won’t see those stray shots very often. You’ll get the extra distance you’ve been wanting, too.


Golf Impact in Ultra-Slow Motion

Here’s a fascinating video of what impact looks like. Notice two things: first, how much the club slows down at impact, especially in the driver swings. A lot of swing speed gets removed when the club meets the ball.

It looks like the club doesn’t slow down when you see players hit on TV, but I’ve read that impact removes about 30% of swing speed (Newton’s Third Law), and this video confirms that number to be in the ball park.

The second thing to notice is what happens to the clubface when the ball is hit off center. Do you see the clubface turning? That’s because impact was off-center. That decreases the distance of the shot, because some of the energy of impact is being used to rotate the clubface.

Note also that the film of the sand wedge does not support the myth of backspin being created by the the ball rolling up the clubface. It’s time to put that notion to rest.

The clubs, in order, are:
Sand wedge

Did you also notice, with the putter, how the ball skids across the grass before it starts rotating?

You might not think that a putt has trajectory, but it does. The skid you’re seeing here is what you want. If your putter face is too lofted at impact, or too delofted, the ball will hop, not slide, and distance will be affected.

Contact between the club and the ball in these shots lasts 1/2,000th of a second.