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 KE

_{rot}= ½ I w^{2}
= ½ (0.4*0.42 kg*(0.11m)

^{2}) * (243.63 rad/s)^{2}
=
60.32 J

Maximum KE

_{rot}= ½ I w^{2}
= ½ (0.4*0.445 kg*(0.11m)

^{2}) * (243.63 rad/s)^{2}
=
63.92 J

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