The Magnus Effect
The tendency for an object to follow a curved path instead of a straight one is known as the magnus effect.
This is due to the generation of a side wards force on a spinning spherical or cylindrical object known as the Magnus force.
The mechanism is rather a simple affair – As the rotating object moves through the air, it pushes the air on side of the ball whilst disturbing and slowing the flow on the other side down.
What this does is, it creates a pressure differential. Faster moving air exerts lesser pressure and slower moving turbulent air exerts a higher pressure. And as a result, the ball experiences a force ( known as the magnus force ).
This force vector points from the higher pressure region to the lower pressure one.
The Aerofoil similarity
If you think about it, it is the same principle as a lift in an aircraft. ( the difference off course lies in the fact that for the Magnus effect to take place, the object must spin )
More the pressure differential, more the lift.
Now an obvious question might strike your mind – What if the wings rotated? I present to you the Flettner Rotor Aircraft which whose wings rotate in order to generate lift.
But sadly, the drag that these things produced were also considerably high rendering them impractical! Ahh..
( If you are interested, check out the No sail boat that Flettner built that actually works and uses the magnus effect )
Magnus effect in sports
Magnus effect underlies various sporting action. For instance that spectacular Ronaldo’s free-kick was a consequence of the magnus effect.
Cricket – Spin Bowling.
Notice the change in direction of the ball during flight.
Tennis – The dreaded Topspin
The ball experiences a downward push as a result of magnus effect.
Baseball – A pitcher’s delight
This pitcher just knows how to rule the game.
You get the idea, right ? Basically, any sport that involves a rotating body, you are most likely to find the magnus effect coming into play.
Have fun exploring this effect in your own unique way and as always have a good one! Cheers!
PC: Royal Institution, Cosmol
*** The phenomenon simplified for the sake of explanation. For those who are seeking out answers from a fluid mechanics and mathematical perspective ( boundary layers, flow stagnation,etc ) check out any standard Fluid mechanics Text.