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 :)

V= r (omega): blog 7 :)

In September, the 'Iolani Dance Team and Marching Band performed in the Aloha Week Parade! :) As if dancing 3.5 miles doesnt sound hard enough, sometimes the roads we dance on have bends and turns! We have to stay in our lines NO MATTER WHAT, so to help us around these turns, we use physics! :)
Linear speed depends on radial distance from the center and rotational speed.
If we are making a left turn, then the dancers on the left side must travel very little, and almost stay in place as we round the turn. The dancers on the right, however, must make long strides while maintaining our straight lines. While both sides have the same rotational speed, the radial speeds are different because the dancers on the right are traveling at a faster speed, with a larger radius.

iMPULSE: blog 6 :)

At the last dance team pool party, the whole team was putting their dancing skills to use when they jumped into the water. Instead of the traditional cannonball, there were countless straddles, aerials, and flips- we drove the lifeguards crazy... :)

Looking back, I realize that not only was that an afternoon of fun, but an afternoon of  physics as well. Since the water slows us down as we deccelerate to a final velocity of 0 m/s, the amount of time it takes is greater than it would be if we were jumping onto a hard surface.
Impulse= force times time
Since the water allows us to come to a stop slowly, the amount of force we feel as we hit the water is minimal. If we were to jump onto a hard surface, then the time it takes to come to rest is much smaller. Since force and time are inversely related, the amount of force we feel when we jump onto a hard surface is much greater. Good thing we dont feel very much force when we jump into water, or some of these jumps would have hurt.

POWER: blog 5 :)

My friends and I have a special tradition where if one of us has a birthday coming up, the rest of the group plans a day of surprises for them. My friend Chelsea's birthday was during the beginning of july, and was the last of our group's sweet 16s. After secretly coordinating the day with her parents, we successfully blindfolded her and led her into the car for the start of our day of surprises :) After the hour long road trip, we finally made it to our destination- WET N WiLD :)

We spent the whole day floating in hurricane bay, sliding down the shaka, and tanning under the sun. What I didn't realize at the time, was that physics was responsible for a lot of the fun we had racing down the waterslides.
Power (Watts) = Work (Joules) over Time (Seconds)
Work is equivalent to net force times displacement, and in this scenario, the net force was equal to the force of the current of the water pushing us down the slides, minus the friction of the floaties against the water and the bottom of the slide. Displacement was equal to the length of the silde (in meters) and the time was the amount of time taken from the beginning to the end of the slide. Because the force of the current was high, the friction was low, the length of the slide was long, and the time it took to reach the bottom was short, the power of the system was HUGE. And we definately felt it on some of these rides...

Overall, it was a REALLY fun day :)