Torque

Today I turned on my faucet. It was exhilarating because I got to use some physics to complete the task. The water surely wouldn't have come out if I didn't use my massive amount of torque. Just to refresh your memory, torque wants to change the state of rotation. Torque is arm length multiplied by force, and although I didn't have much handle to work with, which would be arm length (r), I sure had a lot of force (F) to turn that faucet on. Imagine if I had a longer handle (radius) to turn. The task would be effortless.

If I applied a clockwise force of 200 N on the handle, which has a length of 0.7 m, then I would have had a torque of 140 Nm.

Torque = (force)(arm length)
= F(r)
= (200 N)(0.7 m)
= 140 Nm

Sticky Collision

This past Saturday, I watched some football games on TV. This made me think of some sticky collision problems that we did for physics class. The quarterback was scrambling one way and a defensive lineman tackled him from behind in a sticky collision. This meant that the equation m1v1 +m2v2 = (m1 + m2)vf would be very useful to find out an unknown in this problem. For example, if we wanted to find the final velocity if we knew the mass of the quarterback was 100 at a velocity of 4 m/s and the mass of the defensive lineman was 150 at a velocity of 6 m/s, we would just use that equation to solve it.

(100)(4) + (150)(6) = (100 + 150)vf
400 + 900 = 250vf
vf = 5.2 m/s

Space Needle

This past summer, I went to Seattle, WA and had the opportunity to stand on the observation deck of the Space Needle. This structure is very tall. I didn't know it back then but there is a lot of physics involved in this marvel.

The potential energy of me standing on that observation deck was very big. Using the potential energy formula, PE = mgh, where m = mass (kg), g = gravitational pull, and h = height (m), I could tell that the potential energy was going to be high since g = 9.8 and h = 160 m. If I knew my mass in kg I would tell you the exact amount of potential energy I had but I can't. Nevermind. I found out how to convert my weight into kg. Well, since I am 59 kg, my potential energy is 92,512 J (59 x 9.8 x 160).

Suppose I felt like falling off the Space Needle. My kinetic energy would be very big, too. In fact, at the moment I would hit the ground I would have the same amount of kinetic energy as I had potential energy at the top of the observation deck since energy cannot just disappear or suddenly be added. Instead it changes from potential to kinetic energy.

Since KE = 1/2 mv^2, and KE at the bottom = PE at the top, I was also able to find out that the speed at which I would hit the ground would be 56 m/s if there were no air resistance. Falling from this height would be very painful.

Reflection

This weekend I was wondering about how this Physics class was going, and I decided that it was the most awesomest class ever. Even though it has not even been a quarter yet, I am feeling the full benefits of the class. I see the world as a bunch of rules instead of random happenings. These rules that I have learned so far have helped me to relate to the world better.

Although I don't like tests and homework, I do enjoy doing labs and listening to Mr. Kohara teach us something new. However, I feel that homework enables me to enjoy the labs because I actually know what is going on. Classes are never phun when you don't know what's happening. And despite my anxieties for tests, they are also a necessity because they make sure that we know what we are supposed to know. Since my goal is to get an A and fully understand each concept, I have to really try hard and do good on homework, tests, and quizzes.

I would like to have myself study a little bit more for tests and quizzes so that I can get an A. I feel that I have been doing my best on homework even though there are some nights where I just have no idea how to do the problems. On these nights where I have no idea what to do, I take a very long time doing homework. This is probably the only time that I am not having fun for this class.

Saint Louis

Last night we played Saint Louis in the game of football. There were a lot of big guys on their team so I spent a lot of time on the ground. However, as I lay there on the ground after being blasted by a big Crusader, I thought, "Hey! This is not that bad because this is physics! And physics is fun!"

Big boys, who have more mass than I, have much more inertia, and have the ability to bowl me over with no problem. This means that their bodies are just a little more lazier than mine and their bodies want to resist the change in velocity more than my body.

The only way I was able to save myself from being flattened was if I juked the big guys out like how I did on the kick-offs... sometimes. From physics I learned that a bigger, more inert body would have a harder time changing directions. Therefore, as I saw an opponent ready to hit me at full speed, I would step to the side to get around him. This made him continue in the same direction that he thought I would be. As he failed to block/kill me, I sneakily ran around and thought to myself, "I love physics!"

OR and WA Trip

This past summer I took a trip to Oregon and Washington to visit colleges. From Honolulu, I went to Portland, Oregon by plane. Without counting the small, out-of-the-way stops for food and other small colleges, I then rode a car chauffeured by my parents down to Corvallis to check out OSU. The next day, I went to Eugene which is even farther down south to look at U of O. My parents and I decided to go rafting the next day, so we drove east and came back when we were done. When we were finally ready to leave Oregon towards Washington, which is up north, we took a small detour through Beaverton and Forest Grove to look at Pacific U. From there we drove all the way to Seattle via I-5. When we were finished , we flew back to Honolulu.

Although the total distance I traveled was a lot, the farthest I actually got from Honolulu was only about 2,680 miles which is the distance from Honolulu to Seattle. My trip reminded me of some graphing we did in class where we had to add vectors to get to our final destination. If I decided to add up all the component vectors of my trip through the use of trigonometry or geometry, I would have ended up in Seattle.

Kiti Katsu

Today, I observed my cat make a round trip in the backyard. I saw my cat attempt to chase some birds that were hanging around in the yard. Starting her pursuit around her dinner drop-off area, she began her chase with a constant casual walk and then increased her speed until the birds flew away to a nearby house. As the birds flew, she slowed down until she reached a full stop to stare at the birds. Then, as she heard her dinner touch the ground, she ran back the way she came from by slowly increasing her speed until finally stopping at her food bowl to eat.

This experience reminded me of displacement, velocity, and acceleration. My cat's displacement at the end of her bird pursuit was about 15 meters, and along the way, she varied her velocity and acceleration. If the direction in which she moved as she chased the birds was positive, then she began with a positive velocity with no acceleration. As she sped up, she positively accelerated with a higher positive velocity. Then as she slowed down, she negatively accelerated but still had a lower positive velocity until she finally reached a stop.

Then as she changed direction toward her food, she negatively accelerated since she was speeding up in the backwards direction until she reached her food where she once again had 0 acceleration. During this time, she had increasingly negative velocity since she was speeding up in the backwards direction until reaching her stop of 0 velocity. Her total displacement of the whole trip was 0, but her total distance traveled was about 30 meters.