# Impact and Ball Flight

Optimizing a Driver's Launch Parameters
A lot of clubfitters use launch monitors now to fit the driver to the golfer. A common scenario is to get to a fast maximum, but one that doesn't match the spin and launch angle numbers that are supposed to be optimum. This is followed by tinkering to get to the optimum launch conditions -- usually with little or no additional distance to show for it. Here is why that happens, and what to do about it.

Comparison of Trajectory Programs
This mini-study was provoked by response to my study of launch space surfaces, and my driver fitting recommendations based on that study. The accuracy of the Tom Wishon Trajectory Profiler was called into question. Here I compare the Wishon program to three others, and to measured, real-world data.

The Nine Ball Flights
There is a common diagram in many golf books that purports to show the nine basic ball flights. Unfortunately, that diagram is somewhere between useless and incorrect. Here is a version (actually two versions) of the diagram that correspond to physical reality.

Estimating Slice and Hook
How big a slice or hook will you get from a particular amount of open or shut in the clubface? Here is a way of estimating it, that could even be used on the golf course for precision in working the ball.

Gear effect occurs when a driver strikes the ball, and the impact misses the sweet spot. The result is a rotation of the clubhead that imparts spin to the ball. It answers all kinds of questions, like: why woods are designed with curved faces...  why weight screws may (or may not) give a hook bias...  why a driver gives maximum distance when hit above center on the clubface. I was surprised by a few of the answers myself.

Newton and the Divot
Not many people seem to be aware that the clubhead is deflected downward at impact. The physics is pretty easy, but the fact is obscure. It is a partial explanation of why your clubs have to take a divot.

What wind does to a drive
It is pretty well known that a helping wind doesn't help distance as much as a hurting wind hurts. But by how much? And there are other effects due to wind speed, including a difference in dispersion and asymmetric distances on misses left and right.

Smash Factor - Myths and Facts
Is the maximum possible smash factor 1.5? Sort of. Sometimes. It depends. Specifically, it depends on the characteristics of the club you use, and not just how well the ball is struck.

Ball Position for Maximum Distance
Two ways to increase driving distance are to hit up on the ball (increase the Angle of Attack) and to hit the ball higher on the clubface. Key to both is the proper ball position. The ball must be positioned further forward in the stance and teed higher. This article covers how much forward and how much higher.

What does a golf ball weigh? And Why?
Yes, it weighs just under 46 grams. You probably knew that. Here are the details of  why it does, and how much under 46 grams.

What Matters for Driving Distance?
Reinout Schotman has observed that, statistically from current PGA Tour data, ball speed is a significant factor in driving distance, but launch angle and spin are somwhere between insignificant and zero. Here we explore why this should be.

Spin Decay for a Ball in Flight
How fast does a spinning golf ball lose its spin in flight?

3-Dimensional Launch Conditions from Impact Conditions
Going from impact conditions to launch conditions is a challenge. It's even harder in 3D. Here's my cut at how to do it.
(Math warning! Most of this article consists of deriving equations for launch conditions, and is heavy with trigonometry.)