journal #15

This weekend, when i went to my friend's house, we were talking about why potential energy is mgh. I told them that you could derive it by using G and M and R. Although it was quite a long time ago, i remembered many things like satelite and orbital motions. However, there was one thing that bothered me when we were talking about physics. That is, in regular physics class i heard they draw centripetal force on their free body diagram. I told them centripetal force is an imaginary force (net force) so you arent supposed to put it there. But it seems they are required to draw it out. I told them that if they did that in our class they would get 50 points off for tests/quizes. They also didnt seem to understand centrifugal force but since i already explained it to them and they got it back then, i didnt really want to explain it to them again.
Also, when we went to zippy's, my friend had 1 yen in his wallet. From chemistry experience, we floated it on water. That's when our physics knowledge came in handy to explain how that works. Because the weight of 1 yen coin is smaller than the FB force due to its area, the coin floats.

#14

This week we learned a lot about waves and there are waves all over the world. Not only speed waves, we encounter so many waves in our daily lives. For example, while i was microwaving, i thought about waves because its in fact microWAVE. As waves go through the food, it moves the particles and that makes the food warm up (isnt that right, doc?). We also use waves to transmit the radiowaves and so on. But those are all invisible waves so we dont really notice them around. We notice more of ocean waves and stuff. Waves at the beach is the most commonly known example of a wave. We like to go surf and bodyboard when theres a high amplitude. However, when it has high amplitudes and higher frequency, it is dangerous. If you arent good at swimming like i am and go beach on those days, you have made a fatal error. Waves are fearlful though depending on what kind, it is quite useful. some light waves are pretty dangerous too. Some of them can cause skin cancer. Waves are seriouslly all over the world without any exceptions. Its important to learn stuff like that, right doc?

#13

While i was spinning my pen around (because i was bored while filing out informations for my college apps), i noticed that there was a spring inside a pen (i knew it existed but i didnt really care back then). As i observed that spring, i began to learn the mechanics of it. I was impressed how clever they made that thing. As i was impressed, and before i even knew it, i started to wonder if i can figure out the spring constants and some mechanics that actually enables the pen to work. i designed a experiment just like the lab. Except i didnt have the exact weight for 5g~100g objects, i couldnt really do the same thing as a lab. As a matter of fact, i ruined a spring by putting too much weight on it. It was great how i couldnt really just that pen anymore but its alright because i actually was thinking about physics while i was playing around.

#12

This weekend was pretty awesome since it was four day weekend and there was barely any homework. It was pretty nice getting rest from everything once in a while. Therefore, i didnt really have anything physics related this weekend cuz i pretty much spent all my day at home just sitting around, doing nothing. But on saturday, i went out with my friends again to bryans (doc, you gotta come with us!). But since i already talked about physics of pool, im not going to. I actually want to talk about centripetal force and centrifugal force. while we were driving around, people in regular physics didnt know the difference between centrifugal and centripetal force. some of them even argued theyre the same thing. So i told them that centripetal force is the net force and centrifugal is the imaginary force that you feel. When we got to the curve, i told them there is radially inward acceleration and they nodded. And when everyone started to feel the push towards outside, i yelled "THIS IS CENTRIFUGAL FORCE!"
that was fun

#11

This weekend, i watched couple tv shows that dealt with water. One of them was mythbusters and what they were trying to do was to examine if all those ninja skills were actually possible in real life. They tried walking on water by using wooden panels. The point of that is to increase the volume and area of the object touching water proportional to the mass so it would have higher FB's. It sounds very reasonable and it sounds like it works using the wooden slippers because woods has not that much of a mass but can provide a good volume. However, the plan totally failed because the mass of a human being was too much for that FB created by wooden panels. Perhaps if it had a greater volume then maybe it could work out. So they used styrofoam and made a big shoes out of it. The volume of that shoes was apporoximately .9m cubed or something close to it. Im not sure the exact value but from my estimate, thats the volume. So the guy had totaly of 1.8m cubed as a volume for 2 shoes. And the plan was a success because the volume provided more FB force than the weight.

Physics Journal #10

Today, as i was watching the show Man vs Wild, the idea of using sun as a way to know the direction came across quite often. As i was watching and listening to the logic of that, i remembered that although it looks like sun is moving, its actually the earth that is rotating around the sun. Also, i remembered that earth rotates on its axis once every 24 hours. All of these informations reminded me of the lab we did. As i remembered the lab, i remembered that because theres a satellite in the outer space orbitting around at the same speed as the earth rotates.
Also, in man vs wild, there was a part when he slipped down the ice to move through the places to walk. The friction coefficient must have been very low (both static and kinetic) because he slipped down easily and quickly. I even thought that if we tried to find the speed he was sliding down, we could have just ommitted the friction force/work out of the system. Since i doubt the acceleration was constant, i would choose to use cons. of energy concept to find out his velocity, if i ever do.

Physics Journal #9

this weekend, we xc runners and supporters went to maui to compete in states championship. As a team we ran through the course and coaches made checkpoints about how to attack the course. While we were going through that, one thing caught my attention. When our coach told us to let the gravity do the work goin down the hill, i thought to myself, hey we learned this in physics. So with an intelligent mind of mine (yes you can laugh, doc), i yelled out, "guys, use the mg sin theta!" people in physics understood and laughed and people who didnt take physics needed an explanation so we all explained to the freshmen what we were referring to. we explained to them that the weight is mg and because it was an inclined plane, the net force is going downward parallelly along the surface of the inclined plane. therefore we use the mg sin(theta). Which means, on the other hand, when the runners were running upward, they were fighting back the force, mg sin (theta). Though it is one of the simplest physics we learned so far, it was good to review these kind of stuff.