Physics Journal

last physics journal

2008-05-12T14:34:00.002+09:00

wow, doc, wasnt that fast? this is seriously the last journal that we will be writing...and you dont have to read my stupid journals with crazy grammatical errors anymore lol. anyways, i was watching tokyo drift with my friends this weekend. one thing that came into my mind is, does that thing make you go faster? when you drift, the kinetic friction is acting on you to the max. but when you turn normally, you have difficulties turning due to centrifugal force. i think it depends on the speed you are going into the turn. if youre going to fast that it is so hard to turn normally, then drifting is better. its like that problem about satellites escaping speed. if that tangential velocity is too great, then the object would not form the circular path and instead end up going into the wall, in this case.

29

2008-05-05T15:43:00.002+09:00

when i was microwaving the food, i wondered if we can apply the ideal gas law. for example, if you used one of those ziplock box thing, seal it tightly and throw it in the microwave and heated it, can we apply the law? since PV=nRT, and since microwave raises the temperature, the PV must go up along with the temperature. since the volume is kept constant, well...ideally, so then the pressure better go up. so if you stop and think, there is one awesome thing you could make. you could make an explosion with this! not that i tried this before but wouldnt it be kinda cool to see something like that? this could also be presented by a bag of popcorn. when you heat that, it expands. in other words, the volume goes up because the pressure goes up due to the change in kinetic energy.

28

2008-04-28T18:07:00.002+09:00

i just randomly looked at the sun today and i saw this crazy dude in the parachute (however you spell that). when i saw that guy slowly getting down, i realized how strong that thing must be. basically, you are going down with an acceleration of 9.8 meters per second squared. in other words, the weight force is acting on you and thats g times your mass. that means fatter people would have a greater gravity force acting on him. the air resitance is the other force vector that cancels out the weight force. the force of that is expressed in the equation which i dont really remember but you probably know it, doc, so im not gonna even write it down. anyways, so i thought, that parachute supports all kinds of people, how strong did they make it? i thought about it, and i estimated that the parachute can probably handle more than 3000N of force. because i dont think anyone would weigh more than 300kg...well, if someone did, im pretty sure he wouldnt be moving around anyways. so the maximum force that a parachute needs to handle is around 3000N, i think. well, its some random thought.

27

2008-04-22T18:01:00.002+09:00

i was watching this japanese game show called ninja warriors today. this is a show which contestant are challenged to go through difficult obstacle courses. the reason why this is called "ninja" warriors is probably because it requires many ninja-like agility. as i was watching this show, i noticed that everything was physics-related (though we already know life is full of physics). one of the obstacle was to slide down the inclined slope and hop on to the rope and quickly turn around and jump to the net which is underneath the slide. that was like the inclined slope problem and we can pretty much calculate how fast the athlete would go. also, the rope part is representative of cons. of momentum and energy. the maximum velocity in the x firection is gained at the bottom of the rope so one must release when the rope is at the bottom. however, the energy is lost due to friction and air resistance and whatnots but we can estimate and analyze this whole motion...if we wanted to.

26

2008-04-14T16:04:00.002+09:00

today i noticed/realized something interesting. i probably would have never thought about this if i didnt take ap physics with you, doc. while i was walking around today, i was pushed by a really strong wind. it was so strong i had to pretty much had to lean over and gave a little more strength in each step i take. then i realized, wait a second, how does this happen and how would i calculate this bad boy. i understand air resistance because it is like friction, its just there and you know it since there must be somekind of force to against the force put in. wind, on the other hand, is an interesting force. its just there 24/7 like jack-in-the-box drive thru but depending on the days and time, the strength differs. i just wondered, how the heck does this occur. is it because earth is rotating? how would be calculate how much force a wind exerts on us? it may be quite interesting to figure those stuff out.

25

2008-04-07T17:00:00.003+09:00

again, i will talk about track, doc. there was one thing which i noticed during a track meet. while i was watching one race, i reconfirmed myself that the speed of light is faster than the speed of sound. i was on the other side of the track when the official made a gun shot into the sky. i saw smoke coming out of his gun but i heard no sound until maybe like .3-.5 second later. it was pretty cool, i must say because when i was near the official, the smoke coming out and the sound go off at pretty much the same time. this is probably the reason why the hand time and electronic time for state qualifying time is different. because the timer is some distance away from the starting line, they would have a lag when they start their clock. it probably involves human reaction time and whatnots but whatevers. whereas, when it is done electronically, then there would be almost no lag since there is no human error involved (yay to the technologies).

24

2008-03-17T14:38:00.002+09:00

this weekend, i caught a ride on teh bus to my track meet which was at kamehameha. while i was sitting down in the bus, i noticed couple things that were physics related stuff. for example, i noticed the usage of mirrors. there were mirrors arranged in a manner so that bus driver could see most of the things around him. another thing i noticed was the glass windows which acted like a mirror. while i took a glance at the reflected image on a window, i noticed that the image distance and object distance of the scenery were the same, which was pretty cool. also, i noticed that there were many convex mirrors so that people could see a lot of things around them. after learning how stuff works in physics, life became more fun, doc.

23

2008-03-11T02:41:00.002+09:00

The "Mirage Mirror" is really two parabolic mirrors with identical shapes. One (mirror A (bottom)) lays face-up on the table while the other (mirror B (top)), which has a hole in its center, lays face-down on the first mirror. They are designed so that the focal point of one lies just at the vertex of the other when they are placed on top of one another. An object placed at the middle of the bottom mirror will be at the focal point of mirror on top. Light from the object reflects off of mirror B into parallel paths. This light shines on mirror A, reflects, and converges to the point fA. This light makes a real image at fA. If you look at this point, you'll see the object appear to hover at that point.

22

2008-03-03T17:24:00.002+09:00

this weekend was very key doc. i had a track meet and wow, it was full of physics. take long jump for example, that thing is a great example for kinematic equations. a runner wants to get the greatest x velocity (speed youre running forward) and then get the maximum y acceleration/velocity (height). that's like projectile motion we learned except in the real life long jump there's wind speed, air resistance, what so ever. also, take a look at them spikes. whoever thought of using spikes must know a lot bout physics because they mustve known that more friction on your shoes makes you get the minimum energy loss through impact. another one is discuss throwing. instead of throwing it in a linear motion, they use rotational force because centripetal force and so on gives greater speed and energy to throw. the speed is the tangential speed which the discuss obtained through rotational dynamics. this is why i run track doc.

21

2008-02-25T18:24:00.002+09:00

this week, i played drums for sr. luau and afterwards i wondered how drums worked again. last time, i was wondering about toms and snares and so on but now i started to wonder about cymbals. the drum set i used have 2 cymbal and a hi-hat which is kind of like a cymbal. one of the cymbal is called crash cymbal which is used to make a loud noise at the end of a song or the end of a fill. another cymbal is called ride cymbal which makes a high pitched sound and often used when the song is quiet and slow. hi-hat is used most often and it consists of two cymbal stacked like a pancake with a space inside (because cymbals arent flat, it has curved surface). What i wondered was, what makes these cymbals so different because none of them sounds the same. ride cymbal has the biggest surface area so when i crash it, it makes the dimmest sound. on the other hand, hi-hat though i never tried it, will most likely make the brightest sound when i crash it. but this doesnt explain why ride cymbal has the high pitched noise when i hit a different spot of the cymbal. we need to learn more physics to figure this out doc.

20

2008-02-11T08:28:00.000+09:00

lately, i have been trying to learn how to play drums. it is quite difficult to learn but i still have joy in learning how. One day, it just happened to me and wondered, "hey, drums are perfect example to show what we have been learning this entire time!" First of all, the way drum stick bounces off the drums is the proof of newtons law and the laws of conservation of energy. the energy i put in (both potential and kinetic) to hit the drum is conserved (well not really but kind of). Because of friction, some energy must have turned into heat energy but the more energy i put in, the louder the sound becomes and faster the stick bounces back from the drum which explains this concept of cons. of energy. Also, the tension of the drum deteremines the pitch and frequency of the sound i make. The tighter drums (higher tension) give more higher pitched sound while loosened drums give off lower pitched noise. Not only i learned drums, i was able to review my physics knowledge, Doc!

19

2008-02-05T16:04:00.000+09:00

this weekend i got static electricity hurting my finger while i was pushing my cart. well, it was partly because of my bad habit of dragging my feet as i walk. but anyways, i was walking, and then after walking around for a little while i got back to my shopping cart. when i tried to reach for it and touched the metal part of the handle, i got zapped. it hurt a little but not so much so i kept trying it over and over again until i noticed that someone was watching me do that. anyways, after a while, i began to take this in a scientific way so i can analyze how and what is going on. as i drag my feet, i collect all these charges and i have a concentrated electrostatic energy inside of me. when i touch the metal handle, the electric charges attract one another and thus making the electric energy. its something we just learned so i thought it was interesting doc.

18

2008-01-28T17:08:00.000+09:00

this weekend, my friends and i were practicing for a presentation of a song we are going to do at senior luau. When my friend was playing guitar, i noticed that our physics knowledge could explain how guitar works. It is all about frequency and its relationship with length which we had been learning. as he slides his hand toward the bottom of the guitar, the pitch goes higher and higher because the frequency is greater due to the shortening of the length. after figuring that out, i began to experiment with guitar because i wanted to test it out in real life example. although i had a knowledge, i dont think i really examined a real life situation where that happens and how frequency could affect the pitch. So i examined and experimented and i was satisfied with the results. after examining it, i noticed how clever people were to invent things like this. I wonder if they knew the physics property when they made instruments.

17

2008-01-21T17:17:00.000+09:00

this week was the last week of the first semester/2nd quarter. Which means, for us seniors, the hardest part of the school is over and we just need to worry about keeping up with what we had been doing. this also means that i still need to pay attention to physics properties that occur in our daily lives. First of all, i found it interesting that when you hear radio or tv noise through a phone, you can clearly see the lag. this is clearly because the sound waves are transmitted as radiowaves for phones and that is not fast enough to make is lag-free. i am guessing that the farther you are away from the sender, the more lag it will be and that is physics right there.

#16

2008-01-14T17:04:00.000+09:00

This week was quite intereting. First of all, regualr physics class had their projects and i was helping my friends out. It was interesting how they had to make a car out of mouse trap as their engine. They used their physics knowledge and debated what kind of car would be good. Many of them thought making the wheels frictionless would make the car go farther but i told them the car needs friction in order to even move. Also, many argued that the car should be as light as it could be. However, clay and i both told them it should have a good amount of mass so it has momemtum to keep it going. However, it couldnt be too heavy so that it cant move. I told them to calculate it out but they seemed like theyre just going to just guess and check how it works. I knew right away this is the difference between AP and regular classes. We AP students will definitely calculate it out to see which kind of cars would get maximum efficiency out of the mouse trap before we start building one. It was fun watching them make though.

journal #15

2008-01-07T08:37:00.000+09:00

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

2007-12-10T17:00:00.000+09:00

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

2007-12-03T15:43:00.000+09:00

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

2007-11-26T15:29:00.000+09:00

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

2007-11-19T17:35:00.000+09:00

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

2007-11-12T16:22:00.000+09:00

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

2007-11-05T15:37:00.000+09:00

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.

physics journal #8

2007-10-29T15:23:00.000+09:00

this weekend i experienced the centripetal acceleration. I was inside a car with my friend and we made a turn on one of the intersection. As we turned the corner, i thought about the ideas of centripetal acceleration and started explaining it to my friend. I told him that because we were going at 40 mph on the straight and made a turn with a constant velocity, and with the radius of the intersection curve being about 10m or so, we can calculate the centripetal acceleration. i simply converted 40mph into kmph, which is 40mph*1.6km/mile = 64km/h. Now i could apply that velocity-squared/radius equation and solved for the acceleration, which was approximately 409.6km/hr^2. when i told this fact to my friend who was driving, he was impressed in how fast we were accelerating towards center as we turned. I also explained to him about how important free-body diagram was when dealing with inclined plane problems. Because regular physics students are studying work and energy right now, i was helping him out by teaching what i learned in ap physics. That is, as i said, draw freebody diagram.

Physics Journal #7

2007-10-22T15:02:00.000+09:00

This weekend we went to Hawaiian Bryans and played pool. There were many things i could relate to physics in pool. As a matter of fact, i became better at pool (i think) because of physics. Because we learned that the direction of the target ball after the collision is proportional to the direction of the line that connects centers of cueball's and the target ball's masses, i was able to put in more balls than before because i had better idea of where the ball will go. However, due to friction, spin of the ball, and other extraneous factors, the ball didnt go the way i expected to go all the time. Also, the cue ball didnt always go perpendicular to the direction of the target ball went after the collision. that is probably because the mass of the cue ball is a little greater than the mass of the target ball. Another factor that made the error is probably spin. Because we didnt learn spin of the ball yet, we cant really analyze how that could affect the direction of the ball.
I was also aware of friction force between table and the ball. Without it, the ball would go all over the place without stopping. It would be interesting but it would be stupid to play because you can do nothing other than wait for the balls to go in the pocket.

Physics journal #6

2007-10-15T16:45:00.000+09:00

At senior camp, we played this high calibur table game uniquely designed for the 21st century lifestyle. This game is called bulletball, and the objective of the game is to get the ball (or some kind of object) past your opponent by utilizing your forearm and/or hand. We played 6-man bulletball with water bottle that was provided at the camp. As we hit the bottle back and forth the table, i remembered that i could use my physics knowledge to analyze how this works in physics. As we hit the ball, we are using momentum and impulse. Momentum of an object is greater if the mass is greater and since the bottle we used were much greater than a ping pong ball that we normally use, the momentum was much greater. Also, just like the lab we did, as the bottle came to me, i thought to myself, if i hit the bottle to the other side and assume that velocity is positive, then the velocity of the bottle coming near me is negative. Therefore, if i apply a great force in that, i could hit the ball so much faster to my opponent. So i did apply a lot of force so i could hit the bottle with great velocity and get it past my opponents.

Physics Journal #5

2007-10-08T15:52:00.000+09:00

This weekend, we had our xc meet at kamehameha school. Because of the rain, the ground was insanely muddy and it made us have hard time running the race. Because of the slipperliness, one of our runner fell down right after the race began. When the officials stopped the race because of an unadvantageous start, my friend and i discussed about how this has something to do with physics. We both agreed that the ground has a low static friction coefficient. Because of that, as the force we put in to kick the ground increases, there's higher chance of our shoes slipping on the ground. We discussed on what the best way to deal with this problem. One of my friend said it would be better to run from heel to toe because there would be more surface for the shoe to grip on the ground. However, i disagreed with that because i thought the longer time we have our foot on the ground would increase the chance of our foot slipping. Therefore, i suggested to run on the toes and kicking the ground more perpendicular to the ground than we usually do because if we kick the ground almost perpendicular to the ground, the friction force would be at its max. However, if you ran from heal to toe, it would be difficult to do that because you must exert a force in a backward direction which would lower the normal force which would lower the friction force, making the shoes slip on the ground.

Physics Journal #4: Work

2007-10-01T08:04:00.000+09:00

Work is network times displacement of an object due to the force. this week, we had track workouts for our cross country. I ran 800m interval 8 times, so I ran 6400m (8x800=6400, which is equavalent to running running 4 miles) but my displacement is 0m (because I ran around track which means I ran back to where i started 16 times in total). In physics, our whole workout that we put so much effort on requires no work since the final displacement is 0m. It's a little bit disappointing because it feels like I'm wasting my time doing the same amount of work as not doing anything. Thinking like this made me feel like running on track is a bit retarded because you could just not run still have the same amount of work done from running around track, at least in physics definition. On top of that, it's not really me pushing myself, it's the earth that's pushing me.

AP Physics #3

2007-09-24T15:50:00.001+09:00

We learned more about dynamics this week. We learned about friction force and so on. Running sure is full of dynamics because running also involves friction force (kind of obvious but). In order to run, i need friction. Otherwise it will be impossible to go uphill. What enables me to kick off the ground is friction. When I'm running, i never go past my shoes' max friction force. I know this because I never slip when I'm emitting force as i try to run. If my shoes had very little maximum friction force, i would not be able to put that much force to run.
Also, another example would be the tire of a car. While i was in my friend's car, i noticed that the car's tire's maximum friction force is insane. Insane because the car was parked on a steep hill (around 50-65 degrees compared to flat ground). Normally, objects would slide down the hill but since the tire's friction is great, the car stays where it was parked. I forget but i remembered that in the reading it said that the car's tire's friction coeffiecient was around .87 or something like that.

AP Physics journal: Dynamics

2007-09-17T16:18:00.000+09:00

Just like what we discussed in lectures, i felt the difference in net force while i was going up and down using the elevator. Though i was too shy to explaining to others why we are feeling the difference in weight in the elevator, i went over the reason why in my head.
another example of physics-related thing i experienced this weekend was, again, during the XC race. Because i kick off the ground while going down the hill (in other words, jumping down the hill), i am in the air for a little while. Because i accelerate down due to gravity, while i was in the air, i felt very light (less weight). This is exactly like that elevator example. Because there is a downward acceleration, while im in the air i feel less weight. However, when i landed, i felt extra weight on me. It is because my downward acceleration suddenly went down to no acceleration (deceleration). So i wondered wouldnt going down the hill be a good workout too? i think so lol

First Physics Journal

2007-09-11T13:44:00.000+09:00

Two weeks of physics class had passed and I have managed to survive this course so far. Although I faced many difficulties, I still enjoy learning physics. However, I must say Problem Set #2's last problem was hard...How do you find the range for the shortest range?! Anyways, I'm starting to catch on with this whole equations and all, so hopefully I do good on the next test (none of that stupid mistakes i made in the first one...like thinking that fat line in the middle of the graph was axis lol). I'm guessing that 3D movement is exactly like what we're doing right now except we have three independent equations...or maybe not, who knows lol.

When i was running a xc race on saturday, i was actually calclating the average velocity of the pace i was running in and i tried to find the final velocity and acceleration in order to achieve that increase in velocity. my first mile was 6 min and 26 seconds and the race was 2.6 miles. So in order to run faster than 19 min for 2.6 miles, i had to run 1.6 miles in 12min and 34 seconds. i was actually amazed i was thinking through these kind of things in the race. Unfortunately, i decelerated because i got a side pain right after my first mile so i finished the race poorly.