19 June 2014

Tim Cahill: Goal of the Tournament!

"It's the goal of the tournament!"  My summer research student, Chad Hobson, uttered those words immediately after seeing Australia's Tim Cahill strike as incredible a goal as you are ever to see.  We were watching Netherlands take on Australia in my office,  hoping not only to see some great soccer, but some great physics.  We weren't disappointed as the quality of play was top notch, and there was plenty to dissect from a physics viewpoint.

Just a minute before Cahill's great goal, Holland's Arjen Robben scored an incredible goal of his own.  Firing with his left boot from the left side of the penalty box, he sent Brazuca through the Australian defense as one would thread a needle.  Check out Robben's shot below (click on the image for a larger view).
It appears Australia has a great chance to block the shot, right?  Well, watch Brazuca sneak under the first defender's boot (click on the image below for a larger view).
The ball had only the goal keeper to beat, which it did (click on the image below for a larger view).
What a shot!  We could hardly believe what we had just seen, and then Tim Cahill struck the equalizer.  What's great about the start of the play is the Ryan McGowan met a pass moving almost perpendicular to his run.  He in fact kicked the ball without a single dribble (click on the image below for a larger view).
Not only does McGowan kick the ball just 15 yards (13.7 m) from the halfway line, he is kicking the ball to Cahill (in yellow on the far right above) who will have to catch it while looking into the sun.  Look at the stadium shadow on the pitch!  When thinking about what Cahill did, don't forget that he was staring into the sun.  The view below shows that Cahill was about 9 yards (8.2 m) from the penalty box when McGowan kicked the ball (click on the image for a larger view).
The straight-line distance from McGowan's kick to the point where Cahill catches the ball with his left boot was about 41 yards (37 m).  The ball took a bit more than 2.7 seconds to reach Cahill, and Cahill struck the ball immediately upon receiving it.  He never dribbled the ball; the ball never touched the pitch.  The image below shows Cahill receiving the ball (click on the image for a larger view).
The timing was exquisite!  McGowan was running about 15 mph (24 kph) when he kicked the ball.  He launched it off his boot with a speed of approximately 51 mph (82 kph).  Cahill was running forward at roughly 11 mph (18 kph) when he caught/kicked the ball, which was around 2 feet (0.6 m) off the pitch.  The ball was traveling about 37 mph (60 kph) when it hit Cahill's left boot.  The image below shows a better look at the catch/kick (click on the image for a larger view).
Note the players' shadows.  The ball came right out of the sun from Cahill's perspective.  He kicked Brazuca into the middle of the top crossbar, which then ricocheted into the goal.

If you haven't seen this goal, go online and find it.  It's worth watching!

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