05 July 2014

A Great Luiz Free Kick!

Brazil erupted yesterday when David Luiz sent a free kick into the upper-right portion of the goal in the 69th minute to put Canarinho up 2-0 in its match against Columbia.  Check out the setup below (click on image for a larger view).
Luiz was roughly 34 yards (31 meters) from his target.  The overhead shot below shows that Luiz was slightly left of center on the pitch (click on image for a larger view).
With the Colombian wall set up to defend the left side of the goal (as seen by Luiz), Colombian goal keepr David Ospina is set up in the middle of the goal.  Given the placement of the defensive wall, I don't understand Ospina's placement.  With what's in front of him, Luiz will clearly aim for the upper-right part of the goal.  The image below shows Luiz from the front (click on image for a larger view).
Luiz has opened up his so as to direct the ball toward his right.  He's got a great lean when he plants his left boot.  His right boot will drive up through the ball, giving Brazuca a slight topspin.  The image below shows the kick from the back (click on image for a larger view).
You can easily see Luiz's open hip and the ball heading toward his right.  What is strange is the image of Ospina behind the wall.  Given that the ball took just 1.1 seconds to reach its target, any visual obstruction would have been costly to Ospina.  The image below shows that Luiz put the ball in exactly the right spot (click on image for a larger view).
Ospina got his left index finger on the ball, but it wasn't enough.  My model trajectory is shown below (click on image for a larger view).
Besides the trajectory shadow on the pitch, I show with the light black curve what the trajectory would have looked like without the little bit of topspin.  There were even some slight wobbles from knuckling effects.  Without those lovely aerodynamic influences, the ball would have just missed high.

I calculated a whopping 77 mph (124 kph) launch speed at a little more than 15 degrees off the pitch.  The ball had slowed to about 56 mph (89 kph) when it crossed the goal plane.  It was a powerful and accurate kick that justifiably put Brazil's fans into a frenzy!

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