Riding a Ripstik involves angular momentum. You start out with zero momentum because you're not actually spinning. When you twist your upper body one way, your legs and the board rotate in the opposite direction to keep the angular momentum equal to zero. I'm not sure if you can really see it in the picture, but my brother's body is rotating to the left, so his lower body and the Ripstik rotate (sort of) to the right. Momentum is conserved because there is no external torque acting on you.

Ok, so I tried the spoon/fork/toothpick balancing thing and it actually worked :) It kind of reminded me of the balancing bird that we used for one of the labs. The handle of the fork and spoon are kind of like the bird's weighted wings that are extended below its head. That's why I think the CM is located in the air, between the ends of the fork and spoon (which I guess is the support area). This "experiment" proves that the CM is not always at the geometric center but depends on the distribution of the object's mass. It was also like the lab we recently did where we had to balance a 200 g mass at the 5 cm mark of a meter stick. The torque of toothpick's weight had to equal the torque of the spoon/fork (I think).

I was playing Mariokart DoubleDash this weekend, and I realized that it has a lot to do with centripetal force. It may not be real centripetal force since it is just a videogame, but anyways...Centripetal force is important when making turns. I noticed that I had to apply the brakes a lot to make it around some bends (see the sparks in the picture?). In this case, friction was the centripetal force. My cart would spin out when there wasn't enough friction. The centripetal force was also always directed inward. Mariokart DoubleDash even involves bouncy collisions because you get to throw shells and firebombs at other players. The mushrooms also make you accelerate :)

So, me and my brother were playing darts this week and it made me think of physics. The dartboard was at rest when the dart collided with it. I guess that made it a completely inelastic collision since they "stuck" to each other. That means that although momentum was conserved, there was still a change in kinetic energy. Since our darts really suck (they're the cheap kind with plastic tips; our mom didn't want the wall to be destroyed), sometimes a bouncy collision occurred. The dartboard didn't move because it was nailed to the wall, but the dart rebounded off the wall in the opposite direction. I'm not really sure if this was an inelastic or elastic collision, but I do know that momentum was still conserved.

I was playing foozeball with my brother this weekend and we were having an all out war that involved all five balls. Each individual ball had its own momentum once it was struck by one of our "men" or after it rebounded off one of the walls or other balls. The collisions reminded me of those problems we did in class because once they hit each other, the balls would bounce off each other at different angles. Thanks to Mr. Kohara, I now know that the y-components of each balls's momentum are the same regardless of their different angles. I think all the collisions I witnessed were elastic collisions since foozeballs are kind of like billiard balls. Anyways, my brother completely killed me...I really suck at blocking shots, especially when I have to keep track of five different balls!

Halloween was a lot of fun, even though me and my cousins did have to walk a lot farther to get our usual amount of candy. I swear, some houses turned off their lights as soon as they saw (or heard) us coming. We walked up soooo many hills. I realized we each did work because we had to carry our candy bags up each hill. Since the force and displacement vectors were in the same direction, we all did work. Even though we sort of walked in a zigzag path because we were visiting houses, at the top of each hill, we still would have done the same amount of work if we had walked straight up each hill. In the picture, those of us on the stairs also have a greater amount of potential energy than Chad, Justine, Jodie, and Rayn who are the bottom and have zero potential energy.

Ist Quarter Eval.

Yay! The first quarter is (almost) over! Physics has gotten a lot better...I don't feel so overwhelmed anymore. I had a lot of fun doing the bullseye labs, even though me and Ryan missed every single one! Class was also very entertaining when Mr. Kohara, um, ate it when he was pushing the stool :) Making the projectile movie was also cool because it made me think about the physics in every day life. I thought the first few chapters, with velocity and acceleration graphs, were the hardest. The graphs just really confused me. I did like the last chapter on Newton's Laws though, because it was the one that made the most sense. I think I'm actually getting a little better at doing physics problems and drawing graphs. I hope I continue to improve in the 2nd Quarter! Anyway, overall, the first quarter was really fun :)

Crabbing involves tension and force. I went crabbing in Oregon last summer, and it was really fun! First, you drop your net basket off the side of the boat and let it sink to the bottom. After a period of time, you haul on the net basket rope to bring it back up. Because you pull at an angle, the force has both a vertical and horizontal vector. Tension is also involved because the rope must be kept taut, otherwise the crabs will be able to fall out of the basket. Since the rope touches the side of the boat as you haul up the crabs, there is friction involved too. I had to apply a lot of force to haul up my basket...I never knew crabs could be so heavy :)

My cousin, Sugar, thought it would be fun to hang onto Uncle Chris's foot and have him drag her around. This is an example of friction. Each time my uncle took a step, his force forward had to overcome the static friction between Sugar and the ground in order for him (or Sugar) to move anywhere. When he succeeded in dragging her, that meant he overcame the maximum static friction. Because Sugar is pretty light, it took less force for my uncle to overcome the maximum static friction than it would have if she was twenty pounds heavier. As Sugar was dragged across the ground, kinetic friction was involved since she was no longer at rest.

In this picture, Will, Papa John, my dad, and Uncle Po were all cleaning fish. It was pretty gross, but at the same time, it was also kind of interesting. I found that there are some really nasty jelly-looking things inside a salmon (and it wasn't salmon eggs). Anyway, Will is just about to launch a piece of salmon guts at my mom, who took this picture. The piece of fish became a projectile as it flew towards my mom because it traveled both vertically and horizontally, acted upon by gravity. At its peak, the fish had a vertical velocity of 0 m/s. I would never want to have fish guts thrown at me, but I have to admit, the look on my mom's face was priceless :)

My cousin, Madi, was rocking back and forth in her rocking chair. A rocking chair is an example of simple harmonic motion because it is a repetive movement back and forth at an equilibrium position. An equilibrium position is where the maximum displacement on one side is equal to the maximum displacement on the other. The force of the motion is always aimed at the equilibrium position. Later, another of my younger cousins was pushing her and he accidentally pushed her too hard! Through falling, she became a projectile because she traveled both vertically and horizontally through the air. Everyone was freaking out because it looked like a really bad fall, but luckily she was OK. I don't think she'll be allowed to sit on any more rocking chairs any time soon though!

This is a picture from my brother's birthday party. I don't know why, but my cousins started arm wrestling all of a sudden. This actually involves physics. Arm wrestling all depends on torque. By definition, torque is "that whcih produces or tends to produce rotation". Torque is affected by the amount of force applied to an object to make it turn about an axis of rotation. In arm wrestling, the axis of rotation is the elbow. The amount of torque generated also depends on the distance between the axis of rotation and the place where force is being applied. Torque increases when the force and the distance increases. If you bend your wrist in arm wrestling, you shorten the distance between the hand and the elbow, thereby making it harder for your opponent to create a large amount of torque. I can't remember who won this match, but the face my cousin is making is really funny!

Physics so far has been a very challenging course. Like the little girl in the picture, I'm already panicking about what the rest of the year will be like...if I survive the 1st quarter! The dog in the hotdog bun represents my brain being crushed with all the concepts we've learned so far. For some reason I just can't get my mind around graphing position, velocity, and acceleration. The labs are also pretty complicated sometimes, and I'm horrible with computers so I guess that's got something to do with it. I thought the reaction and hang time labs were fun though (I proved I'm a horrible jumper). Calculating my reaction time also showed me why I'm prone to spilling and dropping things...Anyways, I really hope this stuff gets easier to understand later on and hopefully my grades will improve as well :)

This is a picture from when we went dog sledding. In the picture, the dogs are at rest, but they quickly accelerated to a much faster velocity once they started running. The sled accelerated when it went around the curves in the trail because there was a change in direction. The mass of the sled and its passengers also affects acceleration and velocity. I rode twice, and I found that the sled went faster the first time because there was less people in it. The mass of the dogs and its cargo is also important to the momentum of the sled. The faster the sled is traveling and the heavier mass it has, the harder it is to stop.

These are pictures from my trip to Alaska this past summer when my family and I went halibut fishing. Fishing actually has a lot to do with physics. Casting is a projectile motion because it invovles horizontal and vertical motion. As the line is cast out, the vertical motion of the lure's acceleration is affected by gravity. The length of the rod also affects the velocity and acceleration of the lure. Even the tension and friction of a fishing pole's reel become invovled in reeling in a fish. For halibut fishing, however, we mostly just dropped our lines off the side of the boat so the bait would sink to the bottom. For this action, instead of being a projectile motion, it involves free fall acceleration because the lure just drops down vertically.