Sunday, December 8, 2013

World Cup Physics

In light of the recent World Cup drawing, I wanted to look at the physics behind arguably one of the best players in the world, Cristiano Ronaldo.  He has been recorded to kick at soccer ball at a rate of 60 miles per hour which 96.5 km/h. 96.5 km/h is approximately 26.8 meters/second.  The weight of a standard FIFA soccer ball is anywhere between 420-445 g.  The radius of a standard soccer ball is 11cm which is 0.11m. 

The rotational kinetic energy that a soccer ball has when kicked by Ronaldo:

The angular velocity is w=v/r
                                    w= 26.8 m/s / 0.11 m = 243.63 radians/sec

Minimum KErot = ½ I w2
                        = ½ (0.4*0.42 kg*(0.11m)2)  * (243.63 rad/s)2
                        = 60.32 J
Maximum KErot = ½ I w2
                        = ½ (0.4*0.445 kg*(0.11m)2) * (243.63 rad/s)2
                        = 63.92 J

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