Goodbye

May is a time of goodbyes. Last night was my final quartet concert with Kellie, Steph, and Mirabel (aka the best quartet ever) :(. We have been together for three years, so I am very sad that they are all graduating. We played a Shostachovich quartet that was, well, different. My mom thought it was weird, and I think my dad thought so too. It was definitely a piece of music that was outside the box for all of us, but we all enjoyed playing it. It was also pretty short because Mr. Stark got in trouble last semester since our piece was so long. This is a brief video of our rehearsal before my camera died. After the concert, Kellie drove us to yogurtland, and we had a nice time eating yogurt and talking :)

Tomorrow is the physics exam! So I shouldn't really have to explain the physics in this video since we should all know it already :) Sound waves, frequency, wavelength, all that good stuff. This year really has flown by. I remember the first day of physics clearly, as we all sat innocently in our seats, not yet enlightened on the wonders of physics or aware of the stress that lay ahead. For me, this was the hardest class I have ever taken, but I do not regret taking it. On the contrary, it has been a great learning experience. So goodbye, physics blogs and good luck to everyone tomorrow!

MRI

One of my friends had to get an MRI this past weekend, and I didn't really understand what an MRI was, so I googled it. As it turns out, MRI scans have a lot to do with physics, particularly magnetism. First of all, I learned that MRI stands for magnetic resonance imaging. MRI machines use magnets and radio waves to create a picture of the inner human body.

The magnets used in MRI machines produce a magnetic field between 0.5 and 2 teslas. There are many different types of atoms in the human body, but MRI machines focus on hydrogen atoms. Hydrogen atoms have a large magnetic moment, so when they are placed in a magnetic field, they line up with the direction of the magnetic field.

All of the hydrogen protons will align with the magnetic field in one direction or the other. The vast majority cancel each other out, but, as shown here, in any sample there is one or two "extra" protons.

These extra protons are what create the images. The MRI machines applies a radio wave frequency that is specific to hydrogen, and these radio waves are directed at the part of the body that is being examined. The atoms in this region of the body then absorb the energy from the radio waves, and this causes them to spin in a different direction. Then when the radio wave frequency is turned off, the hydrogen atoms return to their natural alignment and release their excess stored energy. This release of excess energy is essentially what creates the final image that can help doctors diagnose injuries and other health problems.

(information from http://health.howstuffworks.com/mri7.htm)

nearsightedness

I have red glasses, like the pair to the left, because I cannot see things that are far away. Oh and red is my favorite color :) The scientific name for nearsightedness in myopia. So basically, in a nearsighted eye such as mine, the eye is too long, and the light that enters the eye is diffracted too much. This causes images of far away objects to form in front of the retina. A diverging lens can correct nearsightedness because when light passes through a diverging lens, the light rays move away from each other. Then when they enter the eye, it is okay that they are diffracted too much. The lens causes the light rays to focus on the retina, so objects are no longer blurry.

Every year when I go to see my eye doctor, my vision has always gotten worse. It can't be that my eye keeps gets longer and longer every year, so I assume my vision gets worse because the muscles that control the lenses in my eyes are overworked from studying so much during the school year. When I was a kid, my parents always told me not to read in the dark because it would ruin my eyesight. I didn't listen to them. That is probably one of the reasons why I started wearing glasses in elementary school. Studying so much really isn't good for our health!

Today while I was riding in the car with my dad, I was drinking from a bottle of powerade, such as the one pictured above. (except mine was actually red) We all know how difficult it is to drink from a bottle or a can in the car, and today was no exception. I took a nice long sip, but suddenly my dad accelerated, and the red liquid spilled all down my shirt. Fortunately I was not wearing a white shirt. I glanced at my dad and saw him laughing at me, but this time, my messyness had nothing to do with the accident. This time, I could point the accusatory finger of blame at physics. Newton's laws provide an explanation for why the powerade spilled. In fact, this incident is a lot like the pendulum-in-the-car problem we had on a quiz oh so long ago. The powerade spilled out of the bottle for the same reason I was pushed back into my seat when the car accelerated. Both me and the powerade resisted the change in motion. Prior to the acceleration, there was no net force acting on me or the powerade because we were moving at a constant velocity. However, once my dad accelerated, there was a net force because F=ma.

skiing

This is another video from my spring break vacation in canada. I wish i could go back because that trip was so fun. I guess I'll just have to relive the awesomeness through these videos that my mother took :) Even during spring break, I could not escape physics. Early on in the trip while riding a chairlift, the thought crossed my mind that perhaps I should take several videos whilst on the mountain so that once school started again, I would not have to worry about my physics blogs for a few weeks. But alas, this is the last of my skiing/boarding videos, so next week i will have to find something else to write about.

I love to ski :) i especially love to ski FAST! When I ski really fast, the freezing cold wind numbs my face and all I hear is the sound of air whooshing past my frozen ears. It is the most exhilarating sensation in the world, and there's no space in your mind or time to think about anything else.

snowboarding

Over spring break, my family and I went skiing in Canada. I snowboarded for 4 days and skied for the other 2. This is a video of me snowboarding. It was REALLY fun :) There is A LOT of physics involved in snowboarding. Learning how to board is so hard because if your turns are not timed correctly, you will fall down. Your speed also affects how you turn. It's actually easier to turn if you are going faster, but when you are first learning, you don't want to go very fast. I like going down nice green runs (they're the least steep) when I snowboard :) When I ski, my favorite runs are through trees, but I'm not brave enough on a board to attempt tree runs. While I miss Canada quite a bit, I am happy to be home.

egg beaters

This is a video of gingerbread dough that some of my friends and I made during winter break. As you can see, these egg beaters have uniform circular motion! They are following a circular path at a constant velocity. As we all know, uniform circular motion means that there is a net force directed radially inward of magnitude (mv^2)/r. This net force is strong enough to mix all the molasses, flour, and butter together. You can increase the velocity of the egg beaters by changing the setting on them. When you first start mixing the ingredients, the flour is very heavy and thick, so it takes more force to mix it together. Electric current from an outlet supplies the force necessary to turn the egg beaters. When you are finished mixing the ingredients, you can get some of the sticky dough off of the egg beaters by increasing the velocity. You have to be careful not to lift the beaters too far out of the bowl, otherwise the dough will fly all over the place!