We study the motion of a ball hit by a tennis racket. The direction, velocity, and spin of the ball are calculated based on a simple model. The motion of the ball on the surface of the racket is studied by using the Lagrangian method with a constrains. The motion of the ball after a collision is studied as functions of the relative velocity between the racket and the ball, the force on the racket, the mass of the racket, and the tension of the strings. So as to be able to send a ball to a given

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... target, we calculate efficient swing patterns for various conditions of the incoming ball, such as its velocity, angle and the spin.