This past weekend, as I was wasting time before going to work, I was looking at all of my pictures from this school year. I came upon the pictures above are of Erika, Gavin, Jon, Jon, and Me when we went out to the soccer field to kick around the ball. I had no idea we had to do a physics journal this weekend until Erika told me so, and before I knew this I was actually looking at the pictures of us kicking the ball with a physics eye! I recalled in class when Mr. Kohara attempted to demonstrate how a system's angular momentum is "zero" as long as there is no outside torque acting on it. The demonstration was slightly convincing, as he threw a football and told us to watch his feet, and even made Grant and Gavin do it to prove that he wasn't just exaggerating it for the sake of physics. Although I could see what he meant I never fully believed it until I came upon our pictures and realized how when we kicked the ball, our arms went in the opposite direction. Even when Gavin was heading the ball in the last picture, his left leg sticks out behind him. I'm not sure if that's an example of angular momentum being "zero," but it seems like it! Or, at least, he's trying to balance his forward movement of his upper body with the lifting of his leg, thus being an example of center of mass and how different positions change where the center of mass is, causing Gavin to feel the need to use his left leg to compensate his header. I just realized why we would need to keep our angular momentum at "zero" (I never realized it before), because if we didn't we would keep on going in the direction we were spinning! Like momentum, once you get some angular momentum, you tend to keep it. Without our upper body spinning the opposite way, we would keep on spinning in the same direction after the kick! Wow I finally get why helicopters need both rotors! Thanks, Physics! :)
