THE MAGNUS EFFECT
The Magnus effect is the commonly observed effect in which a spinning ball (or cylinder) curves away from its principal flight path. It is important in many ball sports. It affects spinning missiles, and has some engineering uses, for instance in the design of rotor ships and Flettner aeroplanes.
In terms of ball games, top spin is defined as spin about a horizontal axis perpendicular to the direction of travel, where the top surface of the ball is moving forward with the spin. Under the Magnus effect, top spin produces a downward swerve of a moving ball, greater than would be produced by gravity alone, and back spin has the opposite effect. Likewise side-spin causes swerve to either side as seen during some baseball pitches.
German physicist Heinrich Gustav Magnus described the effect in 1852. However, in 1672, Isaac Newton had described it and correctly inferred the cause after observing tennis players in his Cambridge college.
In 1742, Benjamin Robins, a British mathematician, ballistics researcher, and military engineer, explained deviations in the trajectories of musket balls in terms of the Magnus effect.
The Magnus effect explains commonly observed deviations from the typical trajectories or paths of spinning balls in sport, notably association football (soccer), table tennis, tennis, volleyball, golf, baseball, cricket and in paintball marker balls.
The curved path of a golf ball known as slice or hook is due largely to the ball's spinning motion (about its vertical axis) and the Magnus effect, causing a horizontal force that moves the ball from a straight-line in its trajectory.
Back-spin (upper surface rotating backwards from the direction of movement) on a golf ball causes a vertical force that counteracts the force of gravity slightly, and enables the ball to remain airborne a little longer than it would were the ball not spinning: this allows the ball to travel farther than a non-spinning (about its horizontal axis) ball.
In table tennis, the Magnus effect is easily observed, because of the small mass and low density of the ball. An experienced player can place a wide variety of spins on the ball.Table tennis rackets usually have a surface made of rubber to give the racket maximum grip on the ball, to impart a spin.
The Magnus effect is not responsible for the movement of the cricket ball seen in swing bowling, although it does contribute to the motion known as drift in spin bowling.
In airsoft, a system known as Hop-Up is used to create a backspin on a fired BB, which will greatly increase its range, using the Magnus effect in a similar manner as in golf.
In paintball, Tippmann's Flatline Barrel System also takes advantage of the Magnus effect by imparting a backspin on the paintballs, which increases their effective range by counteracting gravity.
In baseball, pitchers often impart different spins on the ball, causing it to curve in the desired direction due to the Magnus effect. The PITCHf/x system measures the change in trajectory caused by Magnus in all pitches thrown in Major League Baseball.
The match ball for the 2010 FIFA World Cup has been criticised for the different Magnus effect from previous match balls. The current ball is described as having less Magnus effect and as a result flies farther but with less controllable swerve.