Breaking the Barrier

A few weekends ago my best friend Katie and I decided to drive around the island - you know, just for funsies :) . As I was procrastinating writing this blog by looking through the photo log of our drive, I came across a video we took when a few of the military jets flew overhead when we were near Wheeler Air Force Base and we heard them breaking the sound barrier. It took me a while to recognize it, but this was perfect for my blog!

The reason we could hear the three jets as they flew overhead was because they were traveling as fast as their own sound waves. This make it so the sound waves piled up on one another in front of the moving object. The sound waves then form a mach cone, or wave cone, which is a cone-shaped disturbance made when an object moves faster than the speed of sound. The surface of the cone is the shock wave and the angle of the cone narrows at greater speeds. Chuck Yeager was the first man to break the "sound barrier" (a term coined by the early fighter pilots who survived when their aircraft approached the speed of sound in a dive and lost all control and told stories about this barrier that if you tried to punch through, you were doomed) back on October 14, 1947.

So had I stopped to think about what was going on when the fighter jets were making noise above us, I probably could have regurgitated all of this information that I knew about traveling at the speed of sound, and breaking the barrier. Buuuuuuuuut, if I had Katie probably would have been disturbed at my nerdy-self so its probably better that I didn't (: .

Earth's Magnetic Field

While walking around my living room trying to figure out what to write about for this physics blog, I decided to stop and yell at my brother to turn down the TV volume so I could think. Turns out that was a good idea because my brother was watching a show about the Earth's magnetic field. The show began by discussing how the Earth's magnetic south pole is near the geographic north. This is why we can use a compass because the tip of the needle is the needle's north pole and is attracted to the magnetic south pole of the Earth at the geographic north pole (that's a mouthful). It also said that in roughly 2500 years, scientists predict that the magnetic poles will switch. This is potentially dangerous because it could weaken the Earth's magnetic field which shields all of humanity from the sun's solar winds. Solar winds contain streams of particles flowing out of the sun at ridiculously high speeds and interfere with communication and navigation systems, impede satellite activity, and change the Earth's atmosphere. To show how the Earth's magnetic field protects us from solar winds by repelling and deflecting the particles, the show used our lab experiment with the donut magnets on a pencil to show how you can try to squish the two together but they won't touch because the same magnetic poles face each other. I though it was really cool that I understood what they were talking about, and had done the experiment - it made me feel like I was a good physics student :)

Now, I know we aren't supposed to use google for pictures, but I looked up the show and found a diagram similar to the one on the show explaining how the magnetic "shield" protects us from solar winds:

Wiring

I live in a old house from the 70's in Hawaii Kai, and I guess when housing was being built back then there were fewer standards that needed to be met. I say this because the genius that wired all of the bedrooms in my house connected them to the fuse box in a series circuit rather than a parallel circuit. While the electrician attempted to explain this to my family (it is a difficult concept to understand, house wiring) this essentially means that there is one path for the current to flow along and goes from one outlet, or resistor, to the next with no alternative route. In other words, if one of the outlets burns out, they all go out. My family learned this the hard way when we had three air conditioners on in the bedrooms at the same time and the power went out because there was too much voltage required, a very high current, low resistance, and overheating. In order to rewire the house properly we learned that we would pretty much have to tear down half of the house so for now, we fixed the burned outlet and carefully watch what is turned on at the same time to prevent this from happening again.

The oulet in my room that burned out because of the electrical overload:

This weekend was my Aunty's 50th Birthday, so to celebrate our family went to her favorite restaurant for dinner. We got there early to decorate the private party room, and it was the job of my cousins and I to strategically place all of the balloons around the room. However, after our physics lab in which we observed static friction after charging a balloon by rubbing it against someones head, I began to chase my little cousin around to show him how cool repelling balloons are.

When I rubbed the balloon against Roman's hair, the balloon picked up extra electrons and had a negative charge because it was charged by friction. Holding it near something neutral, like his arm, polarized the hairs on his arm (positive charges moved closer to the balloon because opposites attract) due to induction because the balloon had a negative charge in one area. The static charge built up and each of the hairs had a positive charge near the balloon, and things with the same charge repel each other. That is why the hair on his arm was standing up - the hairs wanted to get as far away as possible from the other hairs that had the same charge, but closer to the balloon that had the opposite charge. The same concept applied when I rubbed a second balloon on Roman's hair, so that it also became negatively charged, and held it near the other balloon. Because in the spots that were closest together both balloons had a negative charge, the balloons were trying to repel each other because the electrons were trying to get as far away from the other electrons as possible.

Roman thought these physics "tricks" were pretty cool and that I was some kind of magician, but really I'm just a physics student who learned that its not that hard to impress a 3 year old :)

The Musik Express

Now that I'm older, one of my favorite rides when the Punahou Carnival comes around is the Musik Express. However, when I was little, I found this ride very traumatizing. As far as I was concerned, this ride of little cars spinning rapidly in a circle on a tilt were going to make me die tragically. There was some force trying to throw me outwards, especially when I was on the outside edge, and unless I screamed very loudly the entire time my father was going to let me go to my death. At that time, I never understood why my father walked out of the ride like nothing happened and I fulfilled my adrenaline rush until the next carnival. But now I do :)

I was wrong when I thought that there was a force pulling me outward and away from the safety of my seat (Centrifugal force) but I was right that there were forces acting on me and keeping me on the ride (Centripetal force). The force of my weight, my father holding on to me, the friction caused by my seat, and the normal force from the side of the car all added together to create the forces that balanced out the force of the spinning ride. Because the angle of the cars change along different points of the ride, the value of each of these forces (except that of my weight) are constantly changing but could be calculated using the angle and radius from the car to the center.

Now that I understand that what I was feeling was a "fake force" or centrifugal force, I am much less afraid of the Musik Express and my safety riding it. Let's just hope that nothing ever goes so wrong that the Centripetal force never exceed its maximum magnitude - then I might fly out and have something to worry about.