THERE ARE NUMEROUS factors which determine the accuracy of a shot.

When you hit the ball off-center, the racket will tend to twist in your hand. The property of an object to resist twisting is called the polar or roll moment of intertia, defined as the mass of the object times the distance of that mass from the axis squared. (M X d ) If this moment is made larger, the racket will be less likely to twist in your hand.

It can be increased by either increasing the mass at the edges of the frame (as in Wilson's perimeter-weighted rackets) or by making the frame wider (as in the Prince and other oversize rackets). Increasing the width is more effective because the added mass only increases the moment linearly, whereas the moment increases as the square of the width.

The success of any shot will also depend, among other variables, on your reaction time and the arc and quality of your stroke.

For most people, reflex or reaction time is about 0.2 seconds. Since it takes the ball about a full second to travel from baseline, this should not be a problem when playing a groundstroke game. But when serving, several types of timing errors are possible. If you attempt to hit the ball 1 foot below the peak of its trajectory, the ball speed will be 100 inches per second at that point. If your timing is off a little, say 0.01 second, it translates into an error in position on the racket face of 0.01 second X 100 inches/second or 1 inch -- an acceptable margin. But if you throw the ball up very high and then try to hit it at 3 or 4 feet below its peak, you increase the uncertainty since between a 1-foot and a 4-foot fall, the speed of the ball doubles and increases the positioning error to 2 inches.

For groundstrokes, you can minimize timing errors by increasing the arc of your swing. At the instant you hit the ball, your racket is in a certain position in the arc. If you hit the ball early or late, the racket orientation and direction of motion will be different than they would be if the ball were hit at the proper time. The actual angular error is given (in degrees ) by the equation:

57 X timing error X (ball speed + racket speed) / swing radius

The worse the timing error, the larger the angular error. For example, assume that the racket head is moving at about 60 feet/second and the ball is approaching at the same speed (around 40 mph). If you swing the racket with an arc wuch that the impact point of the ball on the strings is 3 feet from the center of the arc (a very short, wristy swing), an error in timing of 0.01 seconds corresponds to an angular error of 11 degrees, which is a 14-degree error in ball direction. This becomes a 19-foot change in the ball's position by the time it reaches your opponent's baseline. This is clearly not acceptable, since the alley is only 13.5 feet from the center of the court.

Clearly, increasing the radius of your swing will improve accuracy and control. And you can reduce the error even further by trying to swing, not in an arc, but in an almost straight line with the follow-through in the desired direction of ball flight.