Center of Human Masses

Last week Friday after school, my friends and I were chilling at our benches in Weinberg. For some reason, Misha, Meatloaf (Jared), Dae (Jon), and me decided to try and see how good we could get at balancing on each other. After a few epic fails, Misha would jump on Meatloaf and I would jump on Misha and none of us would tip over. It was pretty fun. I was pretty surprised that Meatloaf was able to sustain roughly 250 pounds on his back without dying (although, judging by his facial expression in the picture, he came rather close). I then remembered learning about center of mass in physics (actually, I was absent that day). The center of mass of an object is the point at which there is an equal amount of mass on either side such that the object is at equilibrium. Looking at the picture, the center of mass on the x-axis was probably just to the right of Misha's shoulders. If you look down in the picture from that point, it is right near Meatloaf's feet. This means that the equilibrium point was just over a stable point that was supporting all of us. This explains why we did not tip over since the balance point of the three of us was being directly supported by Meatloaf's legs and feet. (Photo credit: Bree Chun)

This picture was taken while I was in New York City for the the Economics Challenge last May. It was taken in a pub-type restaurant in Greenwich Village. It features a game of darts between Braxton Sato and myself. The dart in the outer ring of the bullseye was mine; the dart on the fringe of the board was Braxton's. Unfortunately, we were unable to continue our game. Darts is a game contingent on the laws of physics. When a dart hits the board and pierces it without falling off, the laws of momentum are at work. When the dart strikes the board, it has a momentum equal to its mass multiplied by its velocity. However, when the dart strikes board, the board exerts force on the dart over a period of time. The time multiplied by the average force is called an impulse. The impulse is also the change in momentum. The board exerts a force on the dart, continuously decreasing its momentum, and consequentially, its velocity. This continues until the velocity of the dart is 0. The dart does not bounce off of the board because by the time its forward momentum finally equals 0, it is so far submerged in the board that it is does not bounce off.

Friction: Trick or Treat?

Last Friday, in addition to being homecoming was Halloween. After the game, eating, Ho'olauleia (sp?), and the Burning of the I, my friends and I went trick or treating in Kahala. Outside of the mall, we there was a Longs shopping cart stuck in the mud. Robert climbed into the cart and I tried to pull him out of the grass. We truly are geniuses. However, when I tried pulling the cart wouldn't slide and Robert almost fell out. I was confused. I thought that when I pull an object, the object should move. However, I then remembered friction. Friction occurs when there is a force between two objects preventing them from being slid against one another. The rubber wheels and the dried mud clung together, thus making pulling the cart very difficult. When Robert went in the cart, friction increased. Friction is equal to normal force times the coefficient of friction. Since the coefficient of friction is constant, Robert's 140 pounds increased normal force by approximately 450 Newtons. Thus, our antics were impeded by the phun of friction.

Reflections of the First Quarter of Physics

Physics has been completely different from my expectations of it. I thought that physics would be a really easy course that was conceptual, and not mathematic in nature. I built up these expectations through conversations with former physics students and my own notions about what physics was. To be honest, this was kind of disappointing to me. I have never been a science person, however, I really enjoyed Science 7 and Science 8. I dislike most science classes because they tend to examine physical phenomena in such a mathematical, technical manner that the phenomena themselves become so detached from what we are learning. However, in Science 7 and Science 8, we learned about how things worked, not the formulae that served as mathematical proofs as to why things worked the way that they did. I thought that physics would be focused on learning about the conceptual nature of the laws of physics and how they manifest themselves in the world. Instead, physics seems like basically a harder version of any math course that I have taken at Iolani. Instead of learning why elevators fall in the way that they do, it seems like we just use that example in order to apply mathematical formulae. I don't really understand why we learning that kind of thing. The way I see it, we take math courses every semester at Iolani, so why should physics just be another math course? Except for the lab about getting the ball in the cup, it seems like most of the labs are basically extended math problems in which we must collect the data for the problem, as opposed to just being given it. I wish labs were more like they were in Science 7, Science 8, and even Biology, in which their purpose was to give us hands-on ways of learning and examining the things that we are learning. However, physics has definitely had some very good elements. Unlike most classes, physics can be laid-back and fun. I really like the atmosphere of the classroom, and coming to physics is one of the better parts of my school day. In terms of grades, I am not doing as well as I want to be doing. I am having a hard time incorporating trigonometry (which I haven't taken yet) into the course. I also tend to work sloppily and take more short cuts than is permissible, which seems to be particularly damaging in physics. I think the class might be easier if more time was spent devoted to being taught how to do the problems multiple times.

Newton's Third Law on the Campaign Trail

Yesterday, some of my friends and I waved signs for John McCain, fulfilling part of our APUSH campaigning requirement. We walked around the area near Ala Moana and eagerly waved our signs. However, some angry liberals felt the need to flip us off and yell "#$&% YOU!" This is an example of Newton's Third Law. This law posits that for every action there is an equal and opposite reaction. For example, If I push Preston to the left with 89 newtons, Preston would be pushing me to the right by 89 Newtons. While we were campaigning, angry bird-flipping was equal in severity but opposite in meaning to our friendly waves, shakas, and signs. Who knew that campaigning would turn into a physics lesson?

The Hang Time of My Golf Drive

I love to play golf. Golf is a sport that combines the physical precision that the best of sports require with the leisurely pleasure that any activity should have. Unfortunately, I do not get to golf very often, and thus, I am not a wonderful golfer. When I golf with him, my grandpa keeps a distance finder to measure all of our drives. My best drive thus far has been 205 yards. I am going to use the knowledge in my physics textbook to explain why my arms, which are completely incapable of throwing the ball 205 yards, are able to drive it that far. The answer lies in the leverage that I am able to utilize when I swing the golf club. Because of centrifugal force, the club extended from hands is able to swing much further and faster than my arms do when they are swinging the club. The club is light overall, and yet has a heavy chunk of metal which hits the ball. Therefore, when I hit the ball with a relatively slow, weak swing with a light club, the ball flies 205 yards because the swing multiplies the force of my swing on the club and when the heavy point smashes into the ball, the ball goes further than would be expected.

Acceleration Learned the Hard Way

This past week, my family flew in from California and had a reunion in Kailua. I was supposed to watch my baby cousin for about ten minutes and he was playing on the coffee table in the living room. We were playing a game of sorts in which he would drop a very large toy car and I would catch it immediately. However, after about 3 minutes, I forgot to catch the car and it fell on my toe. It hurt and I may have taught my cousin a word for which he might get in trouble if he repeats. This got me thinking. Why would the car hurt after it fell on my toe but not when it fell on my hand when I caught it? I looked through my physics textbook and discovered that falling objects fall at 9.8 meters per second squared. Thus, it hurt more when it fell on my toe because it was airborne longer, meaning that it was going much faster when it hit my toe compared to when it hit my hand. I also figured out that velocity has a positive correlation with force, accounting for the pain felt when the car hit my toe.