Blog 12: Radio Physics

Just the other day I was at my mom's office doing my homework when I glanced at her ancient radio that she has had forever. I've never paid much attention, but then I realized there is a lot of physics involving the old radio. Unlike most radios now days, this radio shows that the FM frequencies are in megahertz and the AM frequencies are in kilohertz. Before I didn't understand how radio stations were able to broadcast their programs and music, but now I know that they send the sound through specific frequencies. Whenever we change the tuning of the radio to the station we want to listen to, we allow the sound waves of that frequency to enter the radio and be played out by the speakers. The sound waves enter the radio through the antenna and then the radio distinguishes the information and sends it out through the speakers.

Blog 11: Phone Physics

When I was in 4th grade, I used to play with other people's cell phones all the time. I went from playing snake or bowling to playing Mary Had a Little Lamb with the keypad numbers. This past week I realized that I could play this song or Hot Cross Buns because each key in a row had a different frequency, so some were higher than the rest. For example, 1, 4, 7, and * have the highest tones, then 2, 5, 8 and 0 and 3, 6, 9, and # have the lowest tones. Since 1, 4, 7, and * are higher in tone, they have the highest frequency, while 3, 6, 9, and # have lower frequencies. Unlike a piano where when you hold down a key, there is a consistent sound made, but when I hold down a phone key it only makes one beep. This means that the period is very short because not much time is needed to make one vibration. Also I remember on the old Nokia phones, there used to be an application where you could make your own ringtone. Each key would be a different note and you could compose a song with all the keys. In this case, every key had a different frequency.

Blog 10: Magnetic Toys

As I contemplated what I should write about for this blog, I went through my old closet looking for anything that could relate to physics. After finding some old Barbie dolls and Beanie Babies, I found my old magnetic writing board. I remember I used to leave my family messages with this board because that's what Joey and Chandler used to do with their board on their front door of their apartment on Friends. Anyways, before I used to think that the words I was writing or the pictures I was drawing would appear magically and all the writing instruments that came with the board were the only objects that I could write with on the board. One time I lost the pen that came with the board and I was devastated because I thought I could no longer write on the board. Later I realized that I could use any magnet to write on the board because all the writing instruments were actually magnets and where ever I contacted it with the board, the iron shavings would attract to the magnet and illustrate my picture. Also I noticed that the magnets that came with the board were very weak and when I used a stronger refrigerator magnet on the board, the picture appeared darker because more dust was attracted to it. Since the boards are made out of plastic, the magnet cannot stick onto the board, even though it attracts the iron dust. Sometimes if the attraction is strong enough, the magnet doesn't even have to make contact with the board to make the iron dust appear. I can't believe I used to think this was magical, but at least now I can explain the physics behind this toy.

Blog 9: Ceiling Fan Physics

This weekend, as I was thinking of something to write about for this blog, I turned on my living room ceiling fan because the room was pretty hot. As I pulled down on the hanging switch, the fan started spinning, since it was pretty hot I pulled down the switch again to increase the speed of the fan. I realized that the ceiling fan switch is similar to the light dimmer switch we experimented with in our lab. We learned that when you increase the length of a resistor, you increase the resistance too, which affects the amount of current in the circuit because I= v/R. As the resistance increases the current decreases and vice versa, causing the fan to spin faster or slower. Since my ceiling fan starts at a lower speed that increases every time I pull the switch, the length of the resistor must decrease with every pull. After pulling the switch 4 times, the fan begins to slow down because the circuit is broken because the switch is probably touching an insulator instead of a conductor.

Blog 8: Physics That Will Make Your Hair Stand Up

When my team and I played in a summer volleyball tournament in Reno, we experienced a lot of static electricity. Every time we walked through the lobby and touched a metal surface, we would get shocked. We even got shocked every time we went into our huddle after we shook hands with the other team and during a time out. My friend, Ali, was especially affected by the dry air and the static friction. Her hair would often stand up when we played.

Through the past few chapters we have been learning about, I now understand why we get shocked and how drier conditions cause an electric charge to stay in the air. When we dragged our feet on the lobby carpet or ran around the court, we picked up or released extra electrons to or from the floor. This gave us a positive or negative charge, so in order to become neutral again we gave off or accepted electrons from the next object we touch. This static build up happens even here in Hawaii, but we are more likely to get shocked in a drier place like Reno because Hawaii's air contains a lot of water which doesn't hold as much charge as drier air, without water vapor. Ali's hair stood up because they all became charged through static friction, so each strand repelled each other.

Blog 7: More Passing Physics

This past week I had practice almost everyday, so I had a lot of time to reflect about the physics of volleyball. Since we were learning about moment of inertia, I started to apply it to some of my volleyball technique. We learned that objects with the same mass have a greater moment of inertia if they have a large radius, or their mass is more spread apart. When I dive to get a ball, in order to stand up quicker, I either roll to the side and stand up or roll back over my shoulder. These maneuvers require quick rotation to stand up faster. I realized that the more I compact my body when I roll, the faster I can stand up and be ready for the next ball. My rotation would be faster because the radius used to calculate moment of inertia would be smaller, than if if my arms and legs were straight out. This is a picture of me right before I go into a roll.


In dance, we do a similar roll to the roll over the shoulder I do in volleyball, but for the dance row, the goal is to keep your legs as straight as possible. Since this increases the radius for the moment of inertia, this roll requires more torque and is not as fast as the volleyball roll.

Blog 6: Water Slide Fun

This past weekend, I was going through some old photos because I was helping my mom transfer all our files from our old computer to our new one. I came across this picture of me on this waterslide at the old Hawaiian Waters Adventure Park. I realized all the physics going on in this picture. My weight is pulling me down to the slide and there is a normal force from the slide is pushing back on me, but the two forces aren't equal because I am a slide, so the forces affect me at an angle. Also I am doing work and there is change in energy.

At the very top of the slide, when I was waiting for the lifeguard to say that we could slide down, I only had potential energy. I could've calculated my potential energy by multiplying my mass by gravity and the height of the slide. At the base of the slide my energy was entirely kinetic and it was equal to my potential energy at the top of the slide. Also even though I was on a mat and there was water flowing down, there was still some friction that helps determine how much work I was doing. Or I could have calculated my change of potential energy or kinetic energy to find my work.