Studying a golf ball (70 km/h, 6000 rpm, 30 degree angle) in slow motion creating a ballmark, it appears to be two phases with different impact on the golf ball.
In this video a heavily topdressed USGA rootzone with creeping bent and 4% (w/w) organic material, moisture at field capacity.
- From hitting the surface to reaching the lowest point
- From start moving up until leaving the surface
In the first part the ball is reducing speed and backspin when compating or displacing the surface, but the ball is also changing direction and sliding more forward into the front of the ballmark.
In the second part, when the ball no longer travels down and from a point when starts moving upwards, the strongest forces impacting the ball are when ball meets the wall of the front in the ballmark, and due to friction and cushiness of the wall, backspin is changed forward rotation and the ball jumps up at a speed and direction which will determin how far it will fly and roll before stopping. In this phase the sand content is important and will be displace upwards with a visible splash instead of compacted downward as in the first phase.
We know the physical properties of the top 25 mm (1 inch) of the turfgrass is strongly depending on thickness of thatch and mat layer. The sand content, amount organic material and moisture is possible to control to influence the physical properties. We also know different spices of turfgrass develop thatch and mat layers in different ways. And we know turfgrass is influenced by fertilizers and cultivation methods and plant growth regulators etc.
To understand playability in terms of how the green is receiving a golf shot, there is a need to study the dynamics of a ball mark-
Is there a Best Management Practice for a ”drop and stop (D&S)” value for a golf green? Not yet. In the future greens will not only be measured by speed and firmness, but also how they recieve the ball. If a standard approach shot with a wedge is predicted to bounce 3 m and then roll 2 m, it will have a strategic value (D&S 3/2) for tour players, and we all need to know what tour players want to know.