MiRRORS: blog 13 :)

On the college tour this spring break, one of the places we visited was Pier 39. While exploring, my friends and I found a house of mirrors, and decided to go in. Each mirror had an arch over it, and was perfectly positioned so that it seemed as if there were multiple archways. Each archway seemed to go on forever, but we couldnt tell until we came face to face with our reflections if we were going down an actual pathway or facing a mirror. This ties in with physics because we just learned how mirrors work. When light from a source reflects off the mirror towards us, the light travels in a straight line and will take the quickest path to get from Point A to Point B. When we talked to the man who built the house of mirrors, he told us that he used this physics concept to figure out the positioning for all of the mirrors, and said it took him 2 years to build the whole thing. Although it seems like the house of mirrors is large, in actuality the space is very limited and only seems big because we are forced to go around and around in circles.

WAVES: BLOG 12

http://www.youtube.com/watch?v=_f4MpeZDa_s

While we were learning about standing waves, I kept envisioning this scene from the move Miss Congeniality. In this scene, Gracie is playing a glass harp as her talent, and I learned that the glass harp works due to physics. In the glasses, standing waves are produced as the air inside vibrates at one (or more) of the glasses resonant frequencies. The amount of water inside each glass changes the pitch each glass makes, which is why she drank some of the water out of the glass that was out of tune. I found it interesting how we were learning about something that shows up in one of my favorite movies.

iNDUCED CURRENT: blog 11 :)

Current can be induced when flux changes. Flux is equal to (magnetic field)(area )(cos of angle between the magnetic field and area vectors). Induced current can be very helpful, and some devices use induced current rather than current from a voltage source like a battery. When the tsunami warning forced Hawaii into a frenzy, my mom quickly pulled out our for-emergencies-hand-crank-flashlight and kept it close at hand the whole night. Rather than relying on batteries, this flashlight requires you to crank the handle, which powers the flashlight. These devices are crucial at times in which we may lack resources.

ELECTRiCiTY: blog 10 :)

Everyone loves Christmas and the many traditions that accompany the holiday. One such tradition is decorating a tree with a string of lights. What many people don't usually think about is, if one of the lightbulbs go out, why dont the others all go out too? That is all thanks to physics :)

Christmas lights are not all connected in series, but in parallel. The difference is that when lights are connected in parallel, the lights are virtually in their own independent circuits. In a parallel circuit, the voltage difference across each section is equivalent, but the current is not. In a series circuit, because there is only one pathway for charge, the current is the same throughout. Parallel circuits are used because if all of the lights were connected in series, if any one of the lightbulbs happened to burn out, all of the lights would no longer light up because there would no longer be a complete closed circuit for the charge to travel across. 

CHARGiNG BY FRiCTiON: blog 9 :)

http://www.facebook.com/?ref=home#!/video/video.php?v=180999631925246

A few weeks ago, my friends and I got together for a "just dance 2" party. In this video, Zach and Evan are dancing to "Its Raining Men"; while the dance itself was really funny, it was even funnier when people started "zapping" each other. While we were dancing, we became charged by friction. The carpet rubbing against Zach's socks made him extra charged, and showed how rubbing two materials together causes the transfer of charge from one object to another. When two materials rub against each other, one will want to hold on to its electrons, while the other will let go of its electrons.

ANGULAR MOMENTUM: blog 8 :)

http://www.youtube.com/watch?v=2gYEtBwmiPE

Physics affects many aspects of dance, including one of the hardest parts- turns. There are many types of turns: pirouettes, coupe turns, fouette turns, pencil turns, etc. etc. The speeds at which a dancer turns for each type differs- fouette turns are much slower than coupe turns. This is because Angular momentum is equal to moment of inertia times angular velocity, and because angular momentum is conserved. In a fouette turn, a straight leg is extended parallel to the ground. This increases the radius of the dancer, which causes the dancer's moment of inertia to increase, due to the fact that moment of inertia is equal to mass times radius squared. When moment of inertia is larger, then the angular velocity is less. In a pirouette, however, the radius is smaller because the leg is bent so that the foot is at the knee, which means moment of inertia is smaller. The angular velocity of a dancer doing a pirouette is larger than if the dancer were doing fouette turns, which is why pirouettes are faster than fouette turns.
This is a video from Winter Showcase two years ago, and it includes alesicon turns (which are like fouette turns because the leg is fully extended) and goes straight into pirouettes. The change in speed is a little hard to see, but when you are doing the turns, the change in velocity is very noticable.

BANKED CURVE :)