Sybase Open Ball Speed (Page 1)

Beyond the velocities registered by the radar guns on the serve in pro tennis, the team wondered what happened to the speed of the ball after it left the server's racket and after the bounce on the court in the modern game of tennis? And what about the speed of other shots besides the serve? How fast were players hitting forehands, backhands, volleys, overheads and returns of serve?

Many players, even at higher levels, reported their perception that the speed of ball actually increased after the bounce. Basic principles of physics and aerodynamics tell us otherwise--air resistance (drag) and the friction of the ball against the court during the bounce cause the ball to lose velocity. But particularly in pro tennis where the shots travel between the players in a second and even less, it was impossible to observe this with any certainty with the naked eye. Another common perception, often voiced by television commentators, was that a great return of serve, came back to the server faster than the serve itself. But what were the realities of ball speed in pro tennis?

Co-investigator Nasif Iskander developed a piece of software to assist in answering the question. Team members digitized video footage of 3 different Pete Sampras matches from the Sybase Open. The program allowed Nasif to plot the position of the ball in this digitized footage at each point in its flight. From this information, and other known measurements drawn from the geometry of the court, the software program was then able to calculate the speed of the ball over the course of the flight.

Analyzing the hits was where the man hours added up. For example, to analyze one serve involved plotting the location of the ball at about 20 points in the flight for each of two cameras. Groundstrokes could be up to 40 points on each camera.

All told, Nasif analyzed over 50 Sampras hits by plotting over 4000 separate points in the flight of his and his opponents shots. The result was a data base recording the initial speed of the ball on every stroke and comprehensive speed measurements of what happened to this initial speed over the course of the flight of the shot, both before and after the bounce.