light ON

Long weekends are the best! But now it’s Monday night and I have to do all of my homework… I didn’t take much pics this weekend so I thought about what I’d blog as I was getting ready for dinner. Then suddenly, as I sat down, a light went off both in and above my head! My sister had turned on the light above our dining table—reminding me of variable resistors and light dimmers. The light switch for that particular light is a circular knob that you push to turn on/off and turn to adjust the brightness; however there are light dimmer switches can also be used by sliding a lever. In the case of my light, a simple method was devised to adjust light levels: variable resistors. A typical resistor is made of a material that doesn't conduct electrical current well. A variable resistor is made from a resistive material comprised of a stationary and a moving contact arm. In the second picture, I captured the knob and drew its basic components (sorry it's messy..i drew it in on my camera). The total resistance of the resistor in this case is varied by adjusting the distance the current has to flow through the resistive material. In my illustration, the moving contact arm is touching the bottom right portion of the resistor. By turning the knob to the left, the contact arm moves in the counter-clockwise direction; thus decreasing the distance the charge has to travel. So when this occurs, the contact arm is to the left and the charge only has to travel through a small amount of resistive material—brighter light! Similarly, when the contact arm is in a position similar to the one I drew, the light emitted is dimmer because the charge has to move through more resistive material. Physics is so illuminating!

SHOCKing!

Ahh this weekend was exciting! Even though the Cardinals lost (they had it!!), and BJ Penn, well..., it was my bday and there was an extra long Office :D Even thought there was a ton of physics involved, I didn’t get a chance to take any pictures of the fight or game. So, I was thinking of what we were learning in class and dug up this picture from this past spring break. Here’s Remi and me on our uber epic trip, waiting for the Bellagio water show to start. These shows never disappoint—one of them was even set to Andrea Bocelli’s, “Time to Say Goodbye!” And although we thought Vegas wasn’t going to be that fun, since our parents planned that part of the trip..(and we were waiting for Disneyland), we got to see “Love,” and experience physics firsthand. As we learned in class, objects usually tend to be neutral. We included, like to remain in a neutral state, but sometimes charge imbalances do occur. Since objects like to be in neutral states, when they lose their balance of protons and electrons, they want to either lose or gain electrons to return to neutrality. Objects reduce their charge imbalances immediately when their electrons are given the freedom to flow. Getting shocked is an example of this occurance. Here in Hawaii, moisture in the air (caused by our consistently humid climate) reduces charge imbalances on its own so we rarely experience shocks. In places with drier climates such as Las Vegas, however, shocks are common. This difference in weather therefore made us subject to more severe static shocks than the ones felt back at home. One place static electricity was eveident was at our hotel room door. I’ve experienced shocks in Vegas from opening doors before, but none quite as “big” as one of the ones I recieved early one morning. On our last night in Vegas, we stayed out later than usual to take in our last sights of the city. The next morning, I had the hardest time waking up because I was tired and the cool weather just made me want to stay in bed! But I slowly got ready. Dragging myself around the room, I got my stuff together and headed for the door. When I reached out to turn the handle, I felt a shock surge through my body! I realize now that the magnitude of the shock was so great because I was accumulating electrons from the floor each time I dragged my foot on the carpet. By the time I reached the door, my body had a negative charge and wanted to return back to a neutral state. So when I finally came in contact with the handle, the electrons in my body rushed towards the neutral doorknob, resulting in a shock. Static electricity was also evident in my hair. Especially when I brushed it in the mornings, I could “feel” my hairs repelling each other, and see it in the mirror. This effect came from the electrons I received from the carpet as well. So, next time in Vegas, I’m gonna use all of this knowledge of charge to create a monster shock for my sister! ;)

ouch. when physics hits back

This past weekend while at my grandparents’ house, my cousins brought their airsoft guns. So we went to backyard to play with them and shoot some cans and water ballons while we waited for lunch to be ready. Airsoft has a lot to do with physics. The guns which we used were electric and were powered by rechargeable batteries. My uncle said that the batteries power an electric motor that turns a gear box or something which compresses a spring. The tension from the spring is then released, sending the plastic BBs through a chamber and out of the barrel. The tension created in the spring must be pretty immense because those BBs fly right out of those guns! With such small masses, it makes sense that they move so fast. However, a smaller mass leaves the BBs susceptible to wind and stuff which can lower accuracy. So, different masses of BBs are used. But if you think about it, the pellets can’t be that heavy, or else they wouldn’t be able to move quickly or hit far targets, so their amount of KE transferred can’t be that big (E=1/2mv2). This means that BBs aren’t super damaging, when compared to larger paintballs for example. I learned this firsthand when my cousin shot me in the leg. Because of the small mass of the pellet and long distance between me and him and his gun, the shot hurt, but not that much. This makes sense because since the pellets we were using were of a small mass, they had small inertias. And although they were shot at higher velocities than other heavier pellets would be, they also lost speed quickly; therefore minimizing the hurt I felt when the BB finally reached me. The flight and flight path of the pellets also are physics related. When we shot the BBs this weekend, because we were aiming for cans and other things close by, their paths appeared perfectly horizontal. But when shooting the gun at a slightly upward angle the other weekend, I could see the parabolic flight of the pellet. My neighbors own Toys n Joys and my uncle likes to play with the airsoft guns. So the other weekend he brought home an airsoft gun that had this tracking thing so the pellets glowed in the dark! It was a perfectly clear and dark night so we all stopped our football game and told our uncle to get the gun. Standing in his driveway, my uncle aimed the gun kind of upwards and we could see its path clearly...it was parabolic :-) The way the BBs fly is physics too and is at the hand of Bernoulli’s principle—the same principle through which airplanes get lift. Airsoft—more fun thanks to physics.

christmas phun

So this winter break was really fun and thankfully pretty restful…I wish it didn’t have to end so soon :/ But now on to the physics part. During our very cold soccer trip to San Francisco, you couldn’t help but being surrounded by the stuff. Even in our transportation—from our airplane ride into SFO, our van rides to the field, and BART ride into the city, we experienced displacement and acceleration among other things. Our total displacement for our trip for example was zero because we flew a bunch of miles to San Francisco, but flew about the same mileage back to Honolulu (in the opposite direction). While in our vans, we exerted a weight on the road which exerted a normal force back, allowing us to drive on the road. On the BART, we went through both positive and negative acceleration as we travelled in opposite to and from the city (Union Square). And even though we didn’t ride the cable cars this time, we watched them run up and down Powell Street as we went in and out of the stores. These cable cars run on a system of underground steel cables and pulleys, maintaining a constant velocity and tension. The actual soccer portion of our trip also embodied physics. When we struck the ball to make a pass or take a shot, we most of the time hit the ball off center, exerting a torque on the ball and therefore causing the ball to spin. And even though most of us can’t bend it like Beckham (yea that’s us, haha)…we could curve the ball enough for the most part to avoid a defender or play a good cross into the box. So here's us in our van, on the BART, with David Beckham ;) and making a pitstop on the way back to the hotel next to a really pretty tree. Wow that's a lot...I guess I'm feeling picture happy tonight

Back at home physics was present as well. Last night some of my friends and I went to Hawaiian Brian’s and played pool..and I didn’t lose! Well as the cue ball struck another ball, I witnessed an elastic collision and saw energy (almost completely) being conserved…just like in our homework problems. The initially stationary cue ball would move thanks to an outside force (you and your pool stick) then would transfer its kinetic energy to the ball you are aiming for. This exchange along with the help of the friction between the ball and the pool table causes the cue ball to stop and hopefully (if you’re good) the other ball to roll into a pocket.
Merry Christmas and Happy Holidays!

marathon

Yesterday I started the day off extra early to help hand out water to thousands of marathoners. When we got to Triangle Park it was 3:30 and we all began to pour gatorade and water into cups. We broke up into groups of three or four and manned a table. All of the groups then started to stack their five layers of cups, trying to finish faster than everyone else. Everyone was almost done with their first layer when the water stopped working! We had a bunch of hoses attatched to a fire hydrant, and all of them stopped flowing. This made us all kinda nervous since our only job as a thirst aid station was to provide the runners with water/gatorade. Then, after a few phone calls, a Board of Water Supply truck arrived and saved the day. He had to "open up" the fire hydrant or something. But to do this he needed a long metal thing which helped him to provide torque...PHYSICS!! Torque is a force that causes or opposes rotation. In this case, it caused rotation and depended on force and the lengeth of the lever arm. The guy had a hard time at first, but he solved this problem by increasing the length of the lever arm...he increased the distance between his hand on the metal thing and the top of the hydrant. I was amazed how common an application of torque could be and how much easier it can make things. I tried to take a picture of this great display of physics, but the hydrant was right next to a reflective fire orange cone, which was the only thing that really showed up in the picture...but you can kinda see the man and fire hydrant if you look closely. The actual running part of the marathon also related to physics. For example, as the runners ran on the road, they exerted a force (mg) downward as the road gave them a normal (n) force upward. Also when we stacked our cups of water/gatorade, I witnessed center of mass. Of course, my friends and I had no problems stacking our cups without them falling, but some of our sisters stacked cups on the cardboard without any cups below them, causing them to fall. Here are some marathon pics. The one with the gatorade cups is from last year...I didn't get a chance to take a good one yesterday with all of the rain. So here's to great physics and all of those brave marathoners!

lightning BOLT!

All of the rain this Saturday was crazy! Our soccer beach run was cancelled (shucks ;) and instead I spent the day giving admissions tours, going to the movies, and celebrating my friend’s 18th birthday. But the rain reminded me of a huge storm my family and I got caught in this summer. Apparently freak thunderstorms are common in Chicago and the rest of the Midwest, but it definitely was an experience for us. Thunder and lightning is caused by, “the difference in charge between the thunder cloud and the foreign surface, such as a different layer of the cloud or the ground.” Normally the cloud gains a positive or negative charge and when the difference between the two regions reaches a certain point, the air between the charges breaks down, allowing the two surfaces to form a circuit and discharge. The first step in formation of lightning is the gathering of charge in the clouds (Physics of Electromagnetism). As the negative charges collect at the bottom of the cloud, the negative forces in the ground move away from the surface. The negative charges from the cloud then connect with the positive forces on the ground, creating a streamer of light…LIGHTNING! The heat created in the air then quickly expands, forming thunder; which is why you see lightning before you hear the thunder. Taller objects generally lead to a more condensed electrical field, making them more susceptible to lightning. In fact, during this storm, the Sears Tower, the tallest building in the Chicago skyline (and North America!) was hit by lightning. The Sears Tower actually gets hit by lightning quite often, thousands of times each year, which is why it has a lightning protection system. Here is a video and picture I took from my hotel room during the fabulous lightning display. The lightning went on all night, even when the rain stopped—embodying perfect physics the entire time.

fishing for physics

Last weekend a few of our families got together and went to the beach to relax and go fishing—it was really fun! The fishing definitely reminded me of physics. As we cast the lines, I saw motions which resembled parabolic curves. However the patterns were not totally accurate probably because of air resistance and drag. I also thought of mass and friction because of the lead weights we added to the lines. Although we couldn’t actually see the weights and hooks underwater, the mass of the weights created friction with the sandy bottom. This frictional force was greater than the force of the current, allowing the weights to stay still. Tension was the next thing that came to mind. As the fish started to bite, I could see an increase in tension in the lines, making it hard to reel the fish in. In the end we caught a bunch of stick fish, moi, white eels, and some other cool fish. I didn’t get any pictures of our catches, but here are a couple of us at the beach…I think the black things are swans.