Hi Gian,

This is an interesting topic for those that want to know the "whys".  The Magnus effect explains why the ball curves when it is spinning.  If you want to know more take a look at this excerpt.

"The Magnus effect (often called the Magnus force and named after its 1852 discoverer Gustav Magnus) is a lift force of tremendous importance to all athletes who want to bend the flight of a ball. You see the Magnus effect at work in the curved flight path of balls that are thrown, hit, or kicked and at the same time are given a spin. Golfers, baseball pitchers, and soccer, tennis, and table tennis players all employ this effect to curve the flight path of the ball. The game of baseball in particular is made more fascinating by the Magnus effect. The ability of a pitcher to throw curveballs, sliders, screwballs, and knuckleballs that have very little spin—and then have a batter hit these pitches—is the essence of baseball.

The Magnus effect operates in the following manner. As a spinning ball moves through the air, it spins a boundary layer of air that clings to its surface as it travels along. On one side of the ball the boundary layer of air collides with air passing by. The collision causes the air to decelerate, creating a high-pressure area. On the opposing side, the boundary layer is moving in the same direction as the air passing by, so there is no collision and the air collectively moves faster. This sets up a low-pressure area. The pressure differential, high on one side and low on the other, creates a lift force (the Magnus force) that causes the ball to move in the direction of the pressure differential" www.humankinetics.com/

The Magnus effect (often called the Magnus force and named after its 1852 discoverer Gustav Magnus) is a lift force of tremendous importance to all athletes who want to bend the flight of a ball. You see the Magnus effect at work in the curved flight path of balls that are thrown, hit, or kicked and at the same time are given a spin. Golfers, baseball pitchers, and soccer, tennis, and table tennis players all employ this effect to curve the flight path of the ball. The game of baseball in particular is made more fascinating by the Magnus effect. The ability of a pitcher to throw curveballs, sliders, screwballs, and knuckleballs that have very little spin—and then have a batter hit these pitches—is the essence of baseball. The Magnus effect operates in the following manner. As a spinning ball moves through the air, it spins a boundary layer of air that clings to its surface as it travels along. On one side of the ball the boundary layer of air collides with air passing by. The collision causes the air to decelerate, creating a high-pressure area. On the opposing side, the boundary layer is moving in the same direction as the air passing by, so there is no collision and the air collectively moves faster. This sets up a low-pressure area. The pressure differential, high on one side and low on the other, creates a lift force (the Magnus force) that causes the ball to move in the direction of the pressure differential