## Sunday, November 5, 2017

### Soccer Balls Roll

Physics News

Every Sunday morning, I wake up and do the same thing, I go for a run, eat breakfast, and watch soccer. This weekend, I began to think about the rotational motion of a passed soccer ball because a ball when passed rolls without slipping.  I decided to then try and figure out what the average angular velocity, centripetal acceleration, and overall kinetic energy of a passed ball. I guess the average speed of a pass to be 15 mph or 6.7 m/s, and the ball has a radius of 0.22m[1]; therefore I am able to calculate the angular velocity of the ball:

W=6.7/0.22

I also decided to find the centripetal acceleration for the average free kick in soccer:

A= 6.72/0.22

Next, I wanted to figure what the overall kinetic energy of a ball is as it moves over the ground. So, I saw that the average soccer ball weighs 15 oz. or .43 kg. Therefore, one can solve for the kinetic energy of the system.

KE=1/2(.43)(6.7)2+1/2(I)(30.5)
I=2/5(.43)(.22)2
KE=9.78 J

Therefore, a soccer player must due 9.78 J of work in order to pass a soccer ball.

[1] https://en.wikipedia.org/wiki/Ball_(association_football)