Why does a ball slice or draw
Whether tennis, table tennis, baseball, football or golf, all of these sports share one common feature among them: when hit with enough force in a certain way the balls used in them can adjust their trajectory mid-air and fly in any number of curved paths between their point of origin and their destination. This is due to a number of physical features that exist within the balls and can, in many ways, be controlled to your advantage both in these sports and others like them.
The primary reason for this adjustment in direction is due to the fact that the ball’s spin, as it flies through the air, creates a pocket of air with an adjusted density in one particular direction. A ball with a high backwards spin, for instance, creates a pocket of lower density sir above it that allows it to appear to even hover at times as the velocity allows for the air above it to be displaced and create an upward lift. Even at relatively low velocities this can occur, and can be seen even when tossing a small fruit in their air with a slight spin on it.
In many ways this is the same way that modern airplanes function, with wings specially designed to increase the speed of airflow over them while maintaining a set natural speed below in order to create a lifting force that allows for flight. By applying enough force to a ball and generating enough rotation speed in the process this effect can be quite pronounced even over short distances.
By the same function this effect can be used for more than just lift, however. By adjusting the rotation of the ball to either side the pocket of lower density air created by the high speed rotation can be forced to shift in any particular function, thus forcing the ball to travel in any number of desired ways.
Baseball pitchers are particularly accustomed to this phenomenon and actively apply it to many of their throwing styles in order to create varying degrees of curves in each of their throws and thus confuse a batter. Much in the same way do tennis players adjust the spin on the ball they hit in order to add a level of control to the court and confuse their opponent as well as prevent many successful returns from being completed due to the increased difficulty presented through the spin of the ball.