| Ever wondered what made Shane Warne's 'ball of | | | | an aerofoil with a circulation which is generated by |
| the century' drift as much as it did? There is a simple | | | | the mechanical rotation, rather than by aerofoil action. |
| physics explanation for this and it is called the Magnus | | | | In many ball sports, the Magnus effect is responsible |
| Effect. | | | | for the curved motion of a spinning ball. The effect |
| Spin the ball as hard as possible | | | | also affects spinning missiles, and is used in some |
| If you take only one thing from this explanation is | | | | flying machines. |
| that you must spin the ball as hard as possible - | | | | When a body (such as a sphere or circular cylinder) is |
| because when you do strange and wonderful things | | | | spinning in the air, it creates a boundary layer around |
| happen to the ball that will scare any batsman! Spin | | | | itself, and the boundary layer induces a more |
| bowlers who can drift the ball take more wickets | | | | widespread circular motion of the air. |
| than other spin bowlers. | | | | If the body is moving through the air with a velocity |
| What does drift do for a spin bowler? | | | | the velocity of the fluid close to the body is a little |
| Together with flight drift makes the batsman move | | | | greater than the velocity on one side and a little less |
| his head as he follows the ball. A spin bowler wants | | | | than on the other. This is because the induced |
| this as it makes the batsman vulnerable to picking | | | | velocity due to the boundary layer surrounding the |
| the wrong line to play. That is why spin bowlers who | | | | spinning body is added to the velocity on one side, |
| make the ball drift take more wickets than normal | | | | and subtracted from the velocity on the other. |
| spin bowlers. | | | | In accordance with Bernoulli's principle, where the |
| The Magnus Effect Explained | | | | velocity is greater the air pressure is less; and where |
| The Magnus effect is the phenomenon whereby a | | | | the velocity is less, the air pressure is greater. This |
| spinning object flying in a fluid (or air) creates a | | | | pressure gradient results in a net force on the body, |
| whirlpool of fluid (or air) around itself, and | | | | and subsequent motion in a direction perpendicular to |
| experiences a force perpendicular to the line of | | | | the relative velocity vector (i.e. |
| motion. The overall behaviour is similar to that around | | | | |