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How does a soccer ball swerve?
- rjtavares 12y agoPirlo's free kick mentioned in the article: http://gfycat.com/CourteousHatefulBat http://gfycat.com/CourteousHatefulBat Roberto Carlos' free kick: http://www.youtube.com/watch?v=Pl0LHM-33Io http://www.youtube.com/watch?v=Pl0LHM-33Io
- amarcus 12y agoDon't forget this classic Carlos goal - https://www.youtube.com/watch?v=ZnXA0PoEE6Y https://www.youtube.com/watch?v=ZnXA0PoEE6Y
- rbonvall 12y ago(Nitpick: Carlos is not a family name. Roberto Carlos is the full given name. His surname is da Silva Rocha).
- JetSpiegel 12y agoNitpickier: Carlos is not his family name, but there are people with Carlos as family name.
- kokoloko 12y agoNotice how the ball in Pirlo's free kick is barely spinning, goes very fast and the path is very unpredictable. It's called a "Folha seca" and it exploits the turbulences to make the ball drop at the last moment. Very spectacular, but hard to score consistently.
- eyko 12y agoIt's spinning, and the amount of curve matches the amount of speed. The unpredictability comes from the fact that the axis is also spinning, but very slowly. It's hard to get the topspin and rotation on the ball, and still hit the target. But these guys train shots for a living.
- dmoo 12y agoIf you have a few minutes have a look at Juninho, one of the best ever. https://www.youtube.com/watch?v=NesfdRNtwsE https://www.youtube.com/watch?v=NesfdRNtwsE Also don't forget the boots are designed to work the ball, for example http://en.wikipedia.org/wiki/Adidas_Predator http://en.wikipedia.org/wiki/Adidas_Predator
- adestefan 12y agoThis is the same principle that makes a knuckleball drop unpredictably and very, very difficult to control. The way that a great pitcher can control a baseball is amazing to watch. https://www.youtube.com/watch?v=iiSucVCuc8g https://www.youtube.com/watch?v=iiSucVCuc8g
- petepete 12y agoHere's a slightly better quality version of Pirlo's free kick: http://gfycat.com/CompetentDefensiveGosling http://gfycat.com/CompetentDefensiveGosling
- happy4crazy 12y agoHakan Calhanoglu's absurd free-kick from near the half-field line has to rank up there with Roberto Carlos's: http://www.highlighthub.com/hakan-calhanoglu-scores-amazing-free-kick-against-dortmund-video/ http://www.highlighthub.com/hakan-calhanoglu-scores-amazing-...
- nkurz 12y agoThe paper referred to is here: The aerodynamics of the beautiful game by J.W.M. Bush http://math.mit.edu/~bush/wordpress/wp-content/uploads/2013/11/Beautiful-Game-2013.pdf http://math.mit.edu/~bush/wordpress/wp-content/uploads/2013/... one can only be puzzled to note that striking a smooth beach ball or an old, worn volleyball with spin has just the opposite effect I'm having great difficulty believing this. I've spun many beach balls and struck man old, worn volleyballs and have never seen a ball curve the wrong way. I've also dealt with many smooth ping-pong balls, and have even sanded off the dimples on golf balls to see the aerodynamic effect. I'm not saying it's mathematically impossible, just that I didn't think it would be possible to find this effect in the real world. Maybe I've just never tried something smooth enough. Is there some reasonable home demonstration of this that I can try to prove it to myself? They say they did it with a latex band around a soccer ball?
- rcthompson 12y agoIt sounds like the effect depends on whether the surrounding airflow is turbulent or laminar. I believe that making an object smaller biases the airflow more to turbulence, so ping pong balls and golf balls may be too small to show the negative effect at their respective game-relevant velocities. Also, just having a rough surface texture can be enough to cause turbulence, since it causes the air to stick more to the surface. In my experience, ping pong balls have a definite texture to them, and unless you polished that sanded-down golf ball to a mirror finish, it probably has a non-smooth texture too.
- deleted 12y ago[deleted]
- nimaoc 12y agoYou should try it with a lightweight plastic football. They are smooth and really easy to spin so the effect is quite obvious. The more harder you strike it the more it will curl the wrong way.
- foolinaround 12y agoThis effect is also seen in cricket where the new ball and the old ball do different things, and also the ball is actively manipulated (within rules).
- nrzuk 12y agoFootball* :)
- neves 12y agoI thought Hacker News were the only place of the world where soccer weren't a conversation theme.
- JetSpiegel 12y agoRun to the hills!