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.