Falling Cups

This was a weekend of scientific experiement and observation (as well as other forms of procrastination) for me. On Saturday morning as I searched for a sugary snack to eat while I tried to get some homework done before going shopping for prom dresses, I found a can of "all natural" 7UP in my fridge. When I poured it in my glass, I found that streams of bubbles were coming from the same points on the bottom no matter what I did to the glass (no, I didn't turn it upside down). I then hypothesized that there were small irregularities in those spots, as I remeber from Chem that bubbles form on irregular spots, at least when water boils. So I found a glass that my dad had dinked up the bottom by stirring liquid with a spoon and poured the other half of the can in, and found a noticable column of bubbles coming from the center with all the dinks. I have support!!!!! And this was before I really even got into my homework at all. But I know, that's Chem. Here's the simple but funny Physics encounter of the weekend. As my mom and I got home today (Sunday) and were unloading the car of our few purchases and other stuff, my mom brought up the cups of water we had been drinking. To make things easier, my mom stacked two of the cups one inside the other. She then forgot that there were two cups and took hold of the top of the top cup. Normally they would stay together because the static friction force on the two surfaces of the cups was enough to hold up the bottom cup. However, in this case, we did not drink all the water. Therefore, the weight (mg down) of the bottom cup plus the weight of the water was enough to overcome the maximum static friction force dictated by the coefficient of static friction of the cups, creating a net force pointing down. Thus, the cup slipped off, hitting the wood floor of our house with acceleration -9/8 m/s^2 (or g), not leaving a dink but resulting in a large puddle of water on our nice wood floor that had to be wiped up before it hurt the finish. The water splashed out of the cup, obeying the law of conservation of momentum, at least at first, giving the many water droplets large velocities in the same general direction to account for the large velocity and mass of the dropped cup. Thus with these large velocities, the puddle was large as well, for many dropplets flew far away. But no harm done, plus I got to explain to my mom the Physics involved. I felt smart. :-)

Oily Physics

Talk about a Physics packed weekend! I probably saw the most Physics during Family Fair at the game tents, as many of the games relied on projectile motion, especially the Lani Moo, baseball, blast-a-ball, and shoot-the-ring-onto-the-bottle games. However, a knowledge of the workings of momentum and energy are also in order for the plate/octopus dime toss and the floating glass dish + ping pong ball games, as too much energy in the projectile will make it bounce out and you will lose. :-( However, my blog this week is not about Family Fair; it's about the Arizona Memorial. Although I admit that this is perhaps not the best place to be thinking about Phyiscs, I happened to notice that oil was still leaking out of the ship, almost directly below the memorial. However, the first oil that I saw was not rainbow in color; it was white. I first thought that this must be very thin oil, too thin for there to be a phase shift in the two reflecting rays and have constructive interference at any certain color. After seeing a new drop of oil expand into a rainbow of colors and then become this ghostly white sheen on the water, I decided that I was correct. Above I've pictured something like what I saw. However, this oil also led me to another Physic note. Remember the sunglasses from last week? I wore them to Pearl Harbor and Fair. As I was looking at a particularly large area of rainbow, I saw a section in the middle that had no rainbow, appearing as the outside did behind my dark polarized sunglasses. I was curious why this occured and, preparing to try to find out, I picked my head up from a slanted position to strait. But in doing so, I got a better answer than taking off my glasses would have done. As I turned my head, the rainbow disappeared, leaving only the water looking slightly darker than usual, and the ability to see the dark black thick oil floating in the water. I guess the rainbow coming from the thin layer of oil must be polarized, otherwise this would not have worked. I wonder if it is just the light off the oil, or if most light off the water is polarized as road glare is, and that's why polarized sunglasses work so well?

Sunglasses at Night...Late Night

My, we know so much now, don't we? And we've finally hit the long, hard, month of review before the AP exam! Wow. In fact, as I was sitting and reading my online Physics book at my computer before this past test, I discovered some very interesting facts about my computer, and the way I found this out may seem a little strange. If you are wondering about my picture, no I did not just finish watching Blues Brothers or sitting at the beach. In fact, I was trying out my new sunglasses to make sure they were comfortable(I broke my old ones a while ago), with a very inquisitive look on my face. However, this fact combined with a small quirk of mine brought me some valuable Physics insight. Here's the quirk that some of you may have noticed: I sometimes sit with my head inclined to one side or the other, depending on what I'm doing. At this particular time as I sat at the computer and absentmindedly turned my head, I noticed something: the screen changed colors. Or actually it didn't change colors, but it got dimmer. I then remembered that my sunglasses were polarized. As I turned my head to the right, the screen got darker until it nearly disappeared. Then as I turned my head to the left, I found that the position of least change in light intensity occured at just about ninety degrees from the position of darkness. This was consistent with the design of polarized lenses, which have very thin dark bands running either vertically or horizontally depending on their purpose. Because of this, only the vertical or horizontal components of all light waves reaching the lens are allowed to pass through to the eye. Therefore, as I turned my head from the brightest point to the dimmest, more of each light wave was being blocked out until almost all of all light waves were blocked. I've included pictures (yes, I am writing this entry in the background) so you can see what I mean. Cool, isn't it? :-)

Hard Rock Cafe

No, this was not a spring break destination for me, although we did see one. I, as did many of my fellow band-mates, went to Japan over spring break on a great tour with a probably once-in-a-lifetime chance to see the cherry blossoms in full bloom in Tokyo. On our last day, the organization that did our tour treated us to a trip to Uyeno Park to see the many cherry trees there. Although my parents, friends, and I probably collected many hundreds of photos of the trees and blossoms, the one that caught my eye on this Sunday night was a picture my dad took of a sign in the subway station: "Hard Rock Cafe - Uyeno Park." This picture caught my eye for two reasons: one, the small Hard Rock Cafe in a Tokyo subway station was a funny sight, and two, the sign used neon lights to catch people's attentions. And it was these neon lights that caught my attention because of.....Physics! As we learned in Physics, these types of lights are made up of glass tubes filled with different types of gases per tube. When current is run through these tubes, some of the energy in the current goes to exciting the electrons in whatever gas is in the tube. These high-energy electrons then will fall back to their original energy states, releasing a photon of a certain wavelegnth depending on the stregnth of the current and the type of gas in the tube. Were the gas Hydrogen, the electron would be excited to an energy level, then fall back to n=2, corresponding to the Balmer Series and emitting visible light. Each element has different energy levels, therefore releasing different wavelegnths/colors of light corresponding to their emission spectrum. Therefore, there are four different types of gases used in these tubes, one for each different color. Oh no! This means Physics followed me, even on my spring break trip! AAAHHHH!

p.s. just kidding about the screaming :-)

Ripples in the Pool

On Saturday, my mom and I decided to go for a swim at the pool; since swimming season ended, I haven't exercised at all, unless you count our many exhausting but enjoyable band rehearsals, so I needed it. But as I was leisurly walking/floating back to the wall after trying some distance breastroke pulldowns, I thought to myself, "Hey, I wanna try making ripples like in Physics!" I then began playing with my fingers, hands, and the already ripply surface of the water to try to see the two circular waves converge and form higher troughs and peaks due to constructive wave interference, as well as regions of destructive interference. As the waves first began to expand outward, I noticed very large peaks forming, and then more formed, I saw the regions of destructive interference. Had I been able to freeze time and place a sheet of waterproof paper to record the heights at the convergence region parallel to the connection of the radii, I would have seen regions of both constructive (in a 180 degree phase difference with each other, as one peak hits with one trough on the other)and destructive interference. These regions would correspond to the light and dark regions of double slit interference with light as well. Wow, I guess there's one more reason to go to the pool on weekends: Physics in action! :-)

Mirage

In OPTI-GONE Int.'s contraption Mirage, two concave mirrors are placed one on top of the other, with a small opening at the top of one. This contraption forms a floating image inside this opening using the mirrored surfaces inside. After much consideration and learning about concave mirrors, the answer to why this works seems to lie in the focal legnth of the mirrors. When light enters the opening, it hits the object on the bottom, reflecting off the object and radiating out into the mirror region. In the cases of light rays like the ones diagramed, they will bouce a few times, hitting a mirror and refracting at the same angle of incidence, continuing until it either happens to exit the region, perhaps without even touching the object, or hitting the bottom mirror parallel to the principle axis. When it does, the light will then refract to the focal point, which for these mirrors is placed either inside the opening for the bottom mirror or at the center of the bottom mirror for the top mirror. This results in the fact that nearly all light will eventually converge on the focal point at the opening, creating an image to the human eye that should originate in what is actually thin air. The fact that the object sits on a mirror also results in an image of the image of the object on the bottom mirror appearing at the opening as well. Pretty cool!

Infinity Me's!!!!!

When I was little, I had a fascination with mirrors. I guess I liked Physics from a very young age! :-) I had three favorite things when it came to mirrors: two planar mirrors at right angles, two parallel planar mirrors, and three folding planar mirrors of the same size. In my travels through the various malls and dressing rooms of California and Hawaii, I found many instances of all three. But my favorite memory was of a particular dressing room in a department store here (I think it was JCPenny's). I was playing with my three reflections (we were identical quadruplets!) when I discovered that the mirrors, unlike other dressing rooms I had encountered, could move on their hinges and close to form a triangle, just big enough to fit me. :-) When I closed myself in this triangle, I noticed that I increased from quadruplets to quintuplets to sextuplets to septuplets, and so on, until there were infinity me's. However, we were not all in a big circle, there came a point where the number in the circle stopped increasing, and I noticed many other circles around me. It was fascinating. Now that I think back on this experience with some Physics knowledge, I realize what was happening. When I faced a corner, there was an image of me on each of the mirrors, and as I closed them, secondary and tertiary images began to appear as the mirrors reflected each other's light and their images. When the angle was as small as it could get in the triangle, the mirrors stopped reflecting new images. But there were also circles of images coming from the other two corners in the triange, showing me from different sides in the same manner. The mirror opposite each corner would then reflect the image of the circle of me's, then reflect the images of the images from the other mirrors, creating an infinite field consisting of three different orientations of me's. I tried to illustrate my fascinating experience from above(but not with all the reflections, of course!), adding in a pink bow so I could trace light rays. It was very fun. It's funny, I never got into curved mirrors when I was little. Maybe that woudl have been too complicated for me then. Oh well, I still enjoyed mirrors. I wonder where those mirrors are now...