Walter A. “Butch” Kennedy served in the US Army from 1965 to 1968. Shortly after his
discharge he joined the Jacksonville Sheriff’s Office (Florida). During his 17 year law enforcement
career he has worked patrol, traffic and training. In 1983, he was awarded a Medal of Merit for Bravery.
Between 1986 and 1992, he was a full-time instructor at the Institute of Police Technology and Management (Florida).
Walter Kennedy is the author *Conservation of Linear Momentum Using Vector Sum Analysis* and
*Impact Velocity from Conservation of Linear Momentum for the Traffic Accident Investigator and reconstructionist.
*

According to the book description of *Conservation of
Linear Momentum Using Vector Sum Analysis*, it “is difficult for even the experienced reconstructionist
to visualize the momentum components of colliding vehicles. To conquer this problem, W. A. Kennedy has drawn a series of “pictures”
that present a graphic solution to the momentum equations. In this book, the author uses a coordinate system to graphically
illustrate the vector components of the vehicles involved. To clarify the graph, he uses a distinct color for each vehicle
and provides an explanatory text, complete with the momentum formulas and all of the variables needed, to solve the problem.

The graphical solutions provide an alternative to formulas in determining pre-impact and post-impact
vehicle speeds. They also provide a check on the accuracy of computations that use formulas and enable the crash reconstructionist
to gain a clear visual impression of the vector components present in collisions. After a brief introduction, Mr. Kennedy
addresses the following topics: Post-Collision Scene Data and Trajectory Analysis Using the Right Hand Coordinate System;
Vectors and Vector Analysis; Post Impact Analysis; Pre-Collision Scene Data and Trajectory Analysis; Pre-Collision Side of
Equation; Post-Collision Data; and, Trajectory Analysis Using the Left Hand Coordinate System.”