The Pique Turn

In ballet, we did pique turns across the floor. At the time, I was not thinking torque, but there was certainly a lot of physics at work. So...What keeps a dancer from falling?????

To successfully complete a pique turn, there are certain things that a dancer has to be aware of, such as body placement. We say to bend the knee to push off the ground, pull up, have straight legs, hold the arms up, spot so we know where we're going and to not get dizzy, turn the knee out, hold the head up...
and in physics this would mean...!
In the first step, in order to even get up en pointe and balance, the dancer in the picture has to bend her knee. This provides a force for the dancer to push off the ground. This force is also what helps get the dancer to turn...torque!

By step two, the dancer need to have a center of balance, a center of mass. Everything need to be in line over the box of the shoe (which is the part that the dancer stands on). If the dancer leans to much back, side, or front, then she'll fall because her weight would not be on her center of mass.

During the turn, the dancer can't change any of her body position because that would throw her turn off. If she can hold her placement, she can do multiple turns before landing!

When she lands, she needs to continue to keep everything in line over her center of mass in order to land neatly in a fifth position. By bending her knees, the shock of landing is more easily absorded.

Ultimate Frisbee Fun in Physics

This past week we played Ultimate Frisbee for PE in the Upper Gym. It's a very intense game. It also has a lot of physics in it, but I can't yet identify all of what's going on.

Anyway the first thing is the change in momentum when the frisbee is caught. Once the frisbee is thrown in the air, it has momentum, which is mass multiplied with velocity. The change in momentum is the velocity change times the mass. I don't know the frisbee's original velocity when it's flying in the air, but it goes from that to zero m/s, thus changing the frisbee's momentum. Because the frisbee experienced a change in momentum, it also felt impulse, which is force multiplied with time.

During the game, people sometimes collided with each other. For example, a girl was trying to catch the frisbee and score a point for her team, but then the boy on the other team jumped up in the air and caught it before she could. Then when he came down from his jump, he hit her and she fell down. She was stationary, so when he came down, his momentum is transferred to her because momentum is conserved in collisions.

For another example, I tried to intercept the frisbee from reaching the opposite team, so I ran up behind this one guy and he moved back unexpectantly. I had stopped running at that point, so when he moved back, I fell. He had more momentum than me, so I failed to intercept the frisbee. It was also a bouncy collision because he did not fall with me. If he had, then he would not have caught the frisbee.

Ultimate frisbee is a good game, especially when your team wins. By the way, that rectangle on the side of the picture that's blue and white on the inside is supposed to be the door with the stairs that go down by the I Building.

Ballet Yay!

During one Saturday dance class, we all tried to slide into a right/left split while standing up en pointe. It was difficult because we were not doing it correctly and also that we were afraid of falling.

The teacher (who is also a biochemist, i think) explained to us that we needed to put more weight on our back leg so that we would not be pushing into the ground. She also told us that we needed to slide on the side of the shoe rather than the top of the box (the part of the shoe that you balance on).

We were trying to stand on the pointe and slide at the same time, which is hard because then we were pushing our weight into the shoe in an effort to stay balanced. By putting more force down into the shoe, the floor is pushing back, keeping us from sliding. Also, there is more surface area at the point of the shoe as compared to the side of the box, making more friction between the shoe and the floor.

When we tried putting more of our weight on our back leg and sliding on the side of the shoe on the other leg, our back leg could support us while the front foot slid easily across the floor until we fell into a split.

That was rather confusing to explain in writing...It is much easier to show this sort of thing, so I'm sorry if it does not make sense!

Evaluation

So I currently feel a little lost in physics, but not as badly as I was in chemistry. chemistry was much worse. physics is also more interesting than chem. but anyway, I feel like Alice in Wonderland because she gets lost and she wants to find her way back to the normal world.

I have put effort into this course, but I might have been able to put more into it. or maybe not. I think that I might have killed myself in my other subjects if I had tried even harder in this class. It's a feeling sort of like Alice because she tries to find her way back home, but she gets sidetracked really easily if I remember correctly. Does that have any relation to my situation? Hmmm...

I hope I can get better grades next quarter, but I'll be happy just as long as I get grades above B-. yep. I hope that friction quiz didn't strangle my grade to death because that would be bad.

By the way, everyone should read Through the Looking Glass by Lewis Carroll because its a really great story!

More Physics in Football!

Last night was the football game against St. Louis and Iolani won!!! It was 35 to 30 :D It got really intense at the end with the drums...and everyone was yelling "Go Defense!" yep. Anyway, projectiles.

When the person does the kick off for the other team and the band plays "Back in Black", the ball flies in a projectile motion. In a projectile, there are two motions, a horizontal and a vertical motion. The horizontal velocity stays constant throughout because gravity has no effect on it. On the other hand, the vertical velocity decreases at a rate of -9.8 m/s. At the very peak of the ball's motion, the vertical velocity is zero while the horizontal velocity stays the same. As it flies back to the ground, the vertical velocity increases negatively at a rate of -9.8 m/s.

The vertical displacement would be zero if the ball is kicked off the ground and the other team does not catch the ball. However, if the other team does catch the ball, the vertical displacement is the height of the ball when it is caught. The horizontal displacement is the distance it traveled from where it was kicked to where it was caught.

Yep, the game was super exciting at the end! And all the Raiders looked super happy. Today I talked to a friend on the other team and he said he considered quitting football that night. St. Louis must've been very sad.

The Orange Car

I do not actually have an orange car, but I wanted the car to stand out in the picture.

So, I was explaining to my mom what this project is about while we were in the car. I decided to use the car as an example just as we were turning the corner. The car is an example of physics because my mom decelerated as we neared the traffic light. Then as we turned the corner to the right, the velocity changed because we were going in a different direction even if we were driving at a constant rate. The velocity involves both speed and direction. After we turned the corner, my mom accelerated in order to change lanes. Then as we went up a hill, she pressed on the gas peddle to keep the car at a constant speed.

Physics at Football Game

For pep band, I attended the football game for Iolani and Damien. We were playing "Hot Hot Hot." Then as soon as we stopped playing, we heard a lot of yelling. One of the Iolani players was zipping down the field and no one could stop him, so Iolani got a touchdown =D Anyway, there was physics in that!

His displacement was about 35 yards (I don't know the exact amount because I didn't get to see the entire play). Displacement is the direction and distance of the shortest path between an initial and final position, so even if he traveled more than 35 yds while trying to get around other players, his displacement is a straight path. He must have accelerated because after he got out of the crowd of the other players, he could increase his velocity with less people blocking him. He had to decelerate and come close to a stop because one Damien player almost got him. Once he got around that other guy, he accelerated again. It was very exciting, yup.

I drew the picture because I don't have a camera to connect to the computer. The people in white are the Iolani players. The purple people are the Damien players. The guy in the very front is supposed to be holding the football, but it's hard to see.