A Fallen Plant

Today when I was doing homework, it was really windy outside and the windows were rattling. I was worried that something might fall over, and sure enough, I heard a loud “thud” because our bamboo plant in the living room had fallen off the table. It was a pretty strange accident, so I thought about the physics that could have caused the accident. First of all, it was evident that the wind provided a really strong force to push the plant off the table. In addition, when I examined the plant, it was already tilting away from the wind, causing its center of gravity to be too much to the side. With its center of gravity, or center of mass, shifted, it was easier for the plant to fall over. There wasn’t any other force on the other side of the plant, such as a support, keeping its center of gravity/mass in the right place. Therefore, because the plants weight was shifted away from the wind and the wind provided another force in the same direction, the plant had no choice but to fall over, due to physics.

Speed Skating

I was watching TV last weekend, and when I was flipping through the channels, I saw speed skating on one channel. Speed skating made me think of physics once again. In speed skating, there is a lot of physics involved. There’s momentum, uniform circular motion, a pivot point, and air resistance. At the start of the race, the skaters pump their arms back and forth in order to get some momentum going. The momentum helps them to build up their speed. Once they are going pretty fast, it is easy to see that they are moving in uniform rotational motion. However, they are skating around an ellipse, not a circle. Therefore, they have a constant speed while their velocity is changing when they go around the turns. Their velocity stays the same when they are skating the straight a ways. I noticed that when they make a turn, they stick out their inside hand toward the center of the ellipse so that it is easier to turn. I realized that their hand can be a pivot point as they rotate around the turn. In addition, they also keep their hands behind their backs as much as possible in order to make sure that they experience less air resistance. They also keep low when they go around the turns to cut down air resistance. With less air resistance, they can skate at higher speeds. All together, the strategies of winning a speed skating race have a lot to do with physics.

Physics in Jet Skiing

When I went jet skiing for the first time this past Wednesday, I had to figure out the physics involved in it before I could get the hang of it. Some of the concepts involved in this activity are force, acceleration, and rotational motion. For example, you have to apply a constant force on the throttle if you want the jet ski to go at a constant speed. If you vary the amount of force applied on the throttle, the jet ski will end up accelerating and decelerating pretty often. It’s much harder to control the jet ski when its constantly speeding up and slowing down. After I learned how to apply a constant force to it, I had to figure out how much force I should put on the throttle without going too fast. Next, there is also rotational motion involved because there was a three-buoy course set up that we had to follow, and we couldn’t go past twenty feet from the buoys. Therefore, when I turned around the buoys, I had to make sure there was a twenty-foot radius and that my speed was constant so that I stayed in uniform circular motion. By keeping in uniform circular motion, I didn’t make too sharp turns or too wide turns. Finally, I learned how to jet ski based on some concepts I learned in physics.

Physics in the SAT!?

Even when taking a test such as the SAT, there is physics involved. I took the SAT today and I found out that there actually was some physics involved when you write with a number two pencil. For example, when you fill in the bubbles with your pencil, you are creating rotational motion, or uniform circular motion. This means that the speed while you are circling in the answers is constant. There is also a centripetal acceleration force directed inwards at all times that is equal to (mv^2)/r, the radius being the radius of the bubble. Another thing I realized is that there is also pressure involved. Pressure is equal to the force per unit area that is perpendicular to the surface of an object. When you exert a bigger force on the paper with your pencil and your pencil is perpendicular to paper, the mark on the paper will be dark. If you don't press as hard with your pencil and slant it so that it goes down at an angle less than 90 degrees, the mark on the paper will be lighter. So even when test taking, you can think of physics to make sure that you fill in the bubbles as dark as you can and as fast as you can without going out of the bubble.