C Major Scale

Sorry, I don't remember how to rotate videos :( I guess the sound is the most important part though. Anyway, this is what a C major scale on a cello sounds like, though preferably more exactly in tune. I've been wanting to write a blog about the cello for a while now, and since we are currently learning about sound, it seemed like the right time. With most string instruments, a bow is pulled across the strings, which vibrates them and produces sound waves. The strings with a smaller diameter produce a higher sound and therefore waves with a greater frequency. The strings with a larger diameter produce a lower sound and therefore waves with a lower frequency. In orchestra everyday, we tune to an A with a frequency of 440 Hz. Some orchestras tune to an A with higher frequencies, but 440 is the most common. When string players tune, they either tighten the strings, which yields a higher pitch, or they loosen the strings, which creates a lower pitch. When string players place their fingers on the strings, it shortens the length of the string which produces higher notes of greater frequencies.

From the lab that we did on Friday, we learned that when you play a note and then move twelve half steps up, the frequency doubles. If you move twelve half steps down, the frequency halves. To apply that concept here, the second C that is played has a frequency two times that of the frequency of the lowest C, the third C played has a frequency four times that of the frequency of the lowest C, and the fourth and highest C played has a frequency eight times that of the frequency of the lowest C.

Dance Showcase

Last night, I went to dance showcase, so that's what I decided to write my blog about. Sorry about all of the heads. This is a video of a hula that uses pu`ili. There is so much physics in dance, but I'll just mention a couple concepts. As you can see, there are a lot of turns in this particular dance. The friction between the dancers' feet and the ground allows the dancers to pivot and turn. If there was no friction, their feet would just slip and they wouldn't be able to pivot. In this dance, the dancers also tap themselves with their pu`ili and tap their pu`ili against each other. They don't want to hit themselves too hard, so they have to make sure that they don't apply too much force!

This is a video of two of my friends chanting. It is really short because my camera ran out of memory :( Anyway, as we are just beginning our study of oscillations and harmonic motion, this video becomes more relevant. The sound of their voices travels in waves across the gym. My friend Pua, who is on the left, has a higher voice than my friend Daiva, who is on the right. This means that the sound waves the Pua produces have a higher frequency than the sound waves that Daiva produces. However, in this case, their frequencies should be the same since they are theoretically chanting at the same pitch. In the first video, you can also hear the music that the dancers are dancing to. My friends would both kill me if they knew I was using these videos for my blog :)

Before and After

I felt that it was necessary to write my blog about Thanksgiving. I'm sorry my videos are sideways :( Anyway, the video on the left is before, and the video on the right is after. The rest is pretty self explanatory. As you can see, after eating her delicious Thanksgiving dinner, my cousin is too full to do anything. In the second video, when my cousin lies down on the ground, her velocity becomes zero as does her acceleration. If I were to draw a free body diagram of her, the two forces would be mg, pointing down, and normal force, pointing up. They would be equal since the net force is zero. We should have weighed ourselves before and after to see how much the mg force increased by. My bet is 10 Newtons.

To relate this to chapter 14, when my cousin is standing up, like in the first video, the pressure she exerts on the ground is much greater than the pressure she exerts on the ground in the second video when she lies down. This is because the surface area of her feet in the first video is much smaller than the surface area of her body in the second video, and pressure=force/surface area.

A Swing

On Friday we had our fall orchestra concert at Mamiya Theater. It was pretty awesome because we all got out of school at 2:15 :) After we were done rehearsing, Richard, Colin, Leslie and me took a walk and explored the St. Louis/Chaminade campus. As you can see in the picture, we found a swing! It was really fun, but it made Colin and Richard feel sick :( At first, only Leslie and me were swinging on it. When Colin and Richard joined us, I asked, "What is the new mg?" and "What is the tension?". It was then that I realized just how much taking AP Physics B has influenced my everyday life. Never before would I have asked these questions. And then I realized that I could use this for my physics blog, so I took a picture :)

For simplicities sake, lets combine Richard, Colin and Leslie into one mass weighing a total of 300 pounds. That means that the mg force equals 2940 N. Because the net force in the y direction equals zero, The normal force plus the y components of the tensions also equals 2940N. The net force in the x direction also equals zero, (unless they are swinging side-to-side) so the x components of the tension must equal each other. In order to swing, Richard, Colin and Leslie must push off from the ground, which in itself involves even more physics. So much physics, so little time! But here is a brief summary for your enjoyment. :)

Rotational Dynamics - Door Handles

This morning, as I was trying to figure out what to write for my blog, I came up with the brilliant idea to make a video of my front door! It provides a perfect example of rotational dynamics. Torque is a force that causes or opposes rotation, and it is equal to the force times the distance from the axis to the force. T=rF. In this case, the force is applied perpendicularly, so if I wanted to calculate the torque value, I would not have to use trig. In this video, my hand applies the force and the distance to the axis is the distance from my hand to where the lock is, which is the point around which the door handle rotates. So lets say my hand applies a force of 20 N and the distance from the axis to the force is 0.05 m. Multiplying these two values together would give you the torque value, which is this case equals 1 N*m. the torque would have a negative value because the door handle is moving in the clockwise direction, so it actually equals -1 N*m . Here is an example of torque found in my everyday life. Until next week :)

The Common Cold

Germs surround us. While viruses and bacteria do not spread as quickly here in Hawaii as they do in big cities such as New York City (see picture from my trip two summers ago), there are still ever present. Quite unfortunately, I have been sick for the past six days. As I sat in my room trying to figure out what to write my blog about, I couldn't really think of anything because my activities have been greatly limited these past several days. So I decided to somehow figure out a way to relate the common cold to physics, and the only way I could think of doing so was through biophysics, even though I did not really know what biophysics was. After googling "biophysics," I discovered that this is actually a very broad term that encompasses biology, chemistry and physics. One website I found said that biophysics, "explains the biological function of cells, tissues, and organisms in terms of the structure and behavior of biological molecules." (http://www.biophysics.org) I also googled the causes of the common cold so that I could figure out a way to somehow link the two. Cold viruses are the main cause of the common cold. We all learned about viruses in 9th grade. Basically, a virus attaches on to a host cell and releases its genes into that cell.

Now for my primitive attempt to relate all of this to biophysics: Genes reflect the molecular structure of the DNA from which they are made, as seen with the virus's genes. Also, after your body has been infected by a virus, your immune system kicks in. The immune system contains many inflammatory mediators that are released when your body is infected with a cold virus. The function of these inflammatory mediators reflect the molecular structures of the proteins from which they are made. I wish my inflammatory mediators would hurry up the recovery process!!!

JU-NI-OR-SS.

I'm sure all the Juniors would agree with me that this years homecoming was the best EVER. Our lip sync owned and our cheer was awesome :) I've watched the videos of both numerous times on facebook. They're just so good (sigh) The homecoming game was the perfect way to end the week. It was fun and I had the opportunity to spend quality time with some of my friends, hence the picture.

As with all other sports, there are many physics concepts involved in the game of football. Projectile motion, forces, momentum, impulse and collisions to name a few. Projectile motion can be seen in the path of the ball when the quarterback throws it to a fellow teammate.  It seems that football is a game of collisions. In this game, people purposefully run into each other over and over again.  This is why football players must wear heavy padding to protect their bodies.  They collide with a lot of force! You could calculate the momentum of an individual football player if you knew their mass and velocity since p=mv. You could also calculate the impulse when they collide, in a variety of ways actually since J=F△t=△P=m△v. Probably the easiest way would be to find their change in velocity and then multiply that by their mass.   

Gosh I still feel pumped up from last week! It was sheer awesomeness. Now back to regular school :(

Watching TV

This is a picture of two of my friends and me watching a movie. This long weekend gave me the opportunity to fry my brain in front of the television. It was wonderful. On Friday I watched Slumdog Millionaire and yesterday I watched The Patriot. They are both SUPER good movies :) It seems that just like everything else in our everyday lives, there is quite a bit of physics involved in watching tv. I will now attempt to give a rudimentary explanation of these physics concepts. Hopefully by the end of the year, I will have a much more comprehensive understanding of these concepts.

First of all there is the light and images that you see on the tv. Visible light is a type of electromagnetic radiation that we learned about in chemistry last year. The different frequencies of the light waves result in us seeing different colors. There is also the sound that we hear coming out of the tv. Sound also travels in waves and the different frequencies of sound waves result in us hearing different pitches. The amplitude of the wave determines the volume.

Brightness is also a factor in watching tv. In biology, we learned that our eyes contain two types of photo sensitive receptors: Cone shaped and rod shaped. The rod shaped receptors make you aware of changes in brightness whereas the cone shaped receptors make you see colors. There are many more rod shaped receptors in your eye than cone shaped receptors, so our eyes are much more sensitive to brightness than color. There is much more physics involved with the eyeball itself and how exactly we see, but we haven's learned about it yet. Maybe I'll write another blog about watching tv at the end of the year after we have learned about all of this in depth, and then I can feel really smart after I compare it to this blog entry :)

Catch!

So this is a picture of my dog. Her name is Kiki. I was playing catch with her today in my backyard, so that is what I am going to write my physics blog about. Playing catch must of been tiring for her cause she looks wiped out in this pic. Anyway, there are many physics concepts involved in playing catch. First of all, there is the projectile motion of the ball, or actually, in this case it was a rope, but ya. You could use kinematic equations to find any variable. For example, if you know the initial velocity and the time, you can solve for the distance traveled. delta x = initial x velocity * time, so you can componentize the initial velocity to find the x component and then multiply that by the time.

The rope also has kinetic and potential energy. If the ground = zero potential energy, then after you throw the rope, kinetic energy is greatest and potential energy is least. At the peak, potential energy is greatest, so kinetic energy must be least because the law of conservation of energy says that the total mechanical energy stays the same. As the rope starts falling toward the ground, kinetic energy increases and potential energy decreases.

To relate this to what we are currently learning about: If I knew the mass of the rope and its change in velocity, then I could solve for the change in momentum because change in momentum = mass * change in velocity. Then I could find the impulse because impulse equals the change in momentum. These are just some of the physics concepts related to playing catch.

I thought it would be really cool to take a video of me playing catch with my dog, but right when I got my camera out, my dog lost interest in the game :( so typical. But here is the video anyway...you can see the projectile motion of the rope! I hope creepy people don't watch it...perhaps I will delete it after Doc reads this...

This is a picture of our awesome tennis team last year. This past Saturday, I was playing tennis with my fellow teammates, Ali and Jamie. We had been practicing for about an hour when, much to my unhappiness, Coach Suzi ordered us to go and do sprints on the track. Great. I find running such an odious form of exercise, especially on a track. What is fun about running in circles??? That's right, NOTHING. Anyway, we had to obey orders, so off we went to purgatory. It was unbearably hot, but miraculously, I survived.

As I was running around the track for the billionth time, with my chest burning and what felt like a knife in my side, it occurred to me that I could use this for my physics blog I guess there was a silver lining to that very dark cloud after all. As we ran around the track, we ran with a constant velocity. However, periodically, we would sprint a certain distance. When we started to sprint, our kinetic energy increased. As we slowed down again, our kinetic energy decreased. Our potential energy stayed the same the entire time though. If the ground was where h=0, then our potential energy stayed at zero.

There was also air resistance acting on us as we ran around the track. As many of us have noticed however, the recent lack of trade winds is the cause for this hot weather, so there really wasn't too much air resistance. Nevertheless, there was air resistance. It was greatest when we sprinted, since air resistance increases with velocity, and least when we ran slowest, since air resistance decreases with velocity. I could figure out the work done by air resistance if I knew the force of the air resistance and how far we ran. Then I could solve for work using W = F cos (theta) * x. Since air resistance acts in the opposite direction, theta would be 180 degrees.

Yay for physics!

Riding the the Car

Ever since we learned about force and Newton's laws, I have become increasingly conscious of my body's movements during car rides. So I decided to write this particular entry about riding in the car. Here is a picture of my dad's Toyota Rav4, where I spend 30 minutes of my life everyday sitting in the front seat.

Today, as I came home from Youth Symphony rehearsal, I paid close attention to my body movements so that I could document them right here. As we left the parking lot of the UH music department, moving at constant velocity, my body was perfectly at ease, not being forced forward or backward. However, as we approached the stop light at the Dole intersection, I found my body was forced slightly forward as we slowed to a stop. When the light turned green, I found my self being forced back into the seat as my dad accelerated forward. Later, as we waited at the on ramp to the freeway, my dad accelerated more than before, and I was pushed even more forcefully back into the seat. As we exited the freeway, the car in front of us stopped abruptly, so I lunged forward in my seat, slamming into my seatbelt. Finally, we made it safely home.

The reason for all of this is physics! Newton's first law states that an object remains at rest, or maintains constant velocity, unless a net force acts upon it. This explains why my body resisted changes in motion. When my dad stepped on the gas and accelerated, my body was forced back into the seat because it wanted to remain at rest. When my dad suddenly stepped on the brakes and we came to a stop, my body lunged forward because it wanted to remain in motion. This is why buckling up is the law: Physics could kill you if you don't.

Popcorn

This is a picture of me (courtesy of Tiffany :)) attempting to throw a popcorn into the trash can in the physics classroom. (This picture was actually taken after the fact, but that is besides the point.) On Monday afternoon, Richard, Christina, Trisha and me were sitting in Doc's room doing physics and PCH homework while enjoying a nice bowl of popcorn. Unfortunately, I dropped a single popcorn on the ground. Because everyone at school has recently been getting sick, I decided not to eat the fallen kernel. I admit that I am a lazy person, so of course I did not want to walk all the way to the trash can. Instead, I got up and attempted to throw the popcorn into the trash. But alas, the kernel didn't even made it halfway to the targeted can! The reason for this is physics! More specifically, air resistance. We all know what air resistance is, and according to our book it is, "A force that opposes motion in air." Air resistance occurs because when an object moves through the air, it collides with the molecules that make up the atmosphere. Air is not very dense and the molecules are very small, but there are a great deal of them so all together, it results in a pretty big force, which we call air resistance.

One major reason why the kernel didn't make it into the trash can is because of surface area. The kernel had a relatively large surface area, meaning that it collided with more air molecules resulting in a relatively large air resistance. In addition, the kernel had a relatively small mass. The air resistance force itself does not vary with mass, but the effect of air resistance does.

Now for some general background on air resistance: Air resistance is not constant. Instead, it is proportional to the speed of the object. The force created by air resistance is called drag. You can use the equation: FD = 1/2 CpAv^2 to find the drag force, where C = drag coefficient for object, p = air density, A = cross-sectional area, and v = velocity. The shape of an object as well as significant changes in speed determine the drag coefficient. From this equation, you can see what factors determine the drag force on an object.

I guess from now on, I'll have to get up and walk all the way to the trash can when I drop popcorn on the floor, which is inevitable since I am a fairly messy eater.

First Impressions

(<-- This made me giggle :)) Has anyone else noticed that the authors of our physics book have a very interesting sense of humor? There are all these little comments such as “I hope we are not the cause of such aggressive feelings.” I guess it’s good to know that scientists can also have a sense of humor.

Anyway…so far, I have found physics very challenging. It is a lot of work, and knowing the formulas isn’t enough. You really have to understand everything thoroughly. Some people just “get” physics but after experiencing this class for the past several weeks, I am pretty sure that I am not one of those lucky people, quite unfortunately. Coming into this class, I had heard from previous students that AP Physics B was the hardest course they had ever taken. I have not been disappointed. While I have found this course to be difficult, I also find it to be quite interesting and enjoyable (Well, seeing my test grades wasn’t very enjoyable.) I actually don’t mind doing physics homework :) Unlike in chemistry, we can apply physics concepts to our everyday lives! Although I have found this class challenging, I am glad that everyone is so nice and willing to offer help and suggestions. I really appreciate it. :) I wonder if we do any biophysics? I don't even know what exactly that is...the physics of biology? Biology is my favorite subject, so that would be pretty awesome :D

I remember on the first day of school, Doc told us not to focus on grades, but more on learning and understanding concepts, so this is my goal for this class. Although through hard work, hopefully I will also achieve good grades…though this brings to mind the poster in Doc’s room about ineptitude. Did anyone else read it? It’s like, “Sometimes trying just isn’t good enough.” That is kind of a depressing thought…But then there’s that other one about attitude. Something along the lines of, “Attitude is a little thing that goes a long way.” I like that one. Maybe that will be my goal in this class: To face the challenges with determination and a positive attitude :) (this was a little off topic, but i really like those posters)