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Real
Ball
Speed
Pete Sampras has his serve regularly clocked by
the radar gun in the 120 mph’s with serves reaching into the mid 130
mph’s. But how fast is the ball traveling when it reaches the
opponent’s racquet? The answer is about 55% slower. Research on ball
velocity for various shots in tennis has revealed that a tennis ball
slows down considerably from the time the ball is struck to the
moment the opposing player is hitting the ball back. This is due to
air resistance and the effects of friction when the ball hits the
court. Taken together air resistance and the friction of the bounce
on the court reduce a serve hit at 120 mph to an average of just
over 60 mph (see chart below) — about
half the initial velocity. The remaining travel time from the bounce
to the opponent’s hit reduce the speed another 8 mph or 13%. So a
120 mph serve when it leaves the racquet of Sampras is only
traveling about 55 mph when his opponent is return it, a loss of
66mph.
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