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 :)