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bdavis

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  1. bdavis

    Equation Dump!

    By bdavis,

    So lately, our physics C teacher has been making us to equation dumps at the beginning of each class. He would give us 4 minutes to write down as many equations as we could, thus seeing how much we had already memorized and how prepared we were for the upcoming exam. To put down as many equations in those 4 minutes not only requires raw knowledge but also strategy involving.... wait for it... PHYSICS!!!:apple: So, the goal in those 4 minutes was to write down 50 equations. That means you would have to average 12.5 equations per minute. That doesn't sound too bad but writing fast helps. Pressing down hard with the pencil increases the normal force which increases the force of friction, thus slowing down the speed at which you are writing your equations. (F=N(mew)) Friction also takes away energy that could be used to maintain a good pace. The work due to friction (w= Fdcos(180) = -Fd) can be minimized if you don't press down hard and lightly glaze over the paper, making sure your equations are down and that you still have enough energy to write more. Thus, you will attain an optimal number of equations, proving to yourself you are prepared if you know your equations. :banghead)
  2. bdavis
    Believe it or not, rubber bands display the law of conservation of momentum very clearly. When a rubber band is pulled back by a person applying a force to it, it doesn't have any momentum because the velocity of the rubber band is zero. So when the rubber band is released, it gains velocity and therefore has momentum. So then how would this action demonstrate conservation of momentum? Well, the rubber band causes the person who released it to experience a recoil force. Since the rubber band is much less massive than a human, the momentum we gain by shooting the rubber band is almost negligible but it still occurs. Therefore when shooting a rubber band, conservation of momentum is demonstrated.
  3. bdavis

    Skiing!

    By bdavis,

    One activity i love to do is ski. I love the exhilarating feeling of going really fast down a steep incline. But in order to attain a fast speed, one must have good form to minimize AIR RESISTANCE. If someone were to go down a steep trail with their torso revealed with their arms extented out, they will reveal a ton of surface area and thus, the air will have more to make contact with. In turn, that person will not go as fast as they possibly could.

    But if someone has good form that can minimize air resistance, such as tucking their arms and shoulders in and crouching down so less of their body is exposed to headwind, then they will be able to go a lot faster. The air resistance will be reduced and their speed will increase. My knowledge of physics can help me improve my speed and time down the mountain. i knew there were reasonable applications for physics!
  4. bdavis

    Driving on the highway

    By bdavis,

    There are many sharp turns we encounter when we drive at high speeds on the highways. And even just driving straight down a highway, cars can lose control and accidents can happen. Friction is a concept and a force that plays a huge role in keeping cars on the road. The coefficient of kinetic friction, Meu, is what measures the ratio of the force of friction and the normal force of the object on that surface. It can help us find the maximum speed at which the car can stay stable on the road before it will lose contact. The higher the coeficient of kinetic friction, the higher the maximum speed will be before the car loses contact. Ice and water lower the coefficient of kinetic friction because it makes the surface much more slick and slippery. So on a rainy or snowy day, it is best to go slower because getting in an accident is much more likely in those conditions. Friction is definitely a concept that we should consider in our everyday lives to be safe drivers in all conditions on the road.
  5. bdavis
    In our everyday world, mechanics that work with cars in autoshops work with a physics concept that we all know and love: Torque! Cars are working machines that are assembled by many parts and those parts are held together by bolts and screws and lug nuts. Tools such as wrenches and pliers allow mechanics to secure parts by putting the nuts and bolts on the car.



    Torque is equal to the applied force times the radius or length from the fulcrum of the object. (T= Fr) To ensure that a lug nut stays on the part of the car and stays there, a wrench should be used.

    To apply a greater torque, a longer wrench should be used when repairing a car. In an experimental setting, a mechanic may want to pick the best wrench to ensure that a lug nut is securely fastened on a part in the car. If he applies the same force to the end of each wrench, would he be better off using a 18 inch wrench or a 12 inch wrench? Well, the equation shows that if the force is kept constant, Torque is directly proportional to the length of the wrench. The longer the wrench, the greater the torque if the force is kept constant.

    So in the future, if a lug nut isn't staying properly fastened on your car, using a longer wrench may be very helpful.
  6. bdavis
    Our year has come to an end. College is in the near future and rapidly approaching with each passing hour. At the beginning of the year, I walked into physics c excited but not really sure what to expect nor was I sure how difficult the material would be. As the year progressed, I realized that the tests were hard and I needed to study harder than I ever needed to before. After I failed two out of the first four tests, I was motivated to do well on the next one. The first rotational exam came and I got the highest grade in the class. I proved to myself and my classmates that I could excel if I put the work in. The rest of the year I did decently on the remaining tests and spread my attention towards my other AP classes as well. Electrostatics and magnetism in the second half of the year was very difficult for me. I tried extremely hard to grasp the vague concepts; visualizing the actions of subatomic particles was difficult but by the time the AP exam came, I felt like I understood it better than I ever had. Going into college, I hope to take more physics courses because it intrigues me. But at the same time, I will also take the lessons I learned with me: don’t procrastinate, read the text book, ask a lot of questions, and take the initiative to study a little each night before each test so I don’t stress myself out and go into each test confident and prepared. College will be hard but I am ready to work hard in order to achieve the success I envision. I will discover the cure for cancer, buy my physics c teacher a silver Porsche, and I am ready to take the next step in education and in life.
  7. bdavis

    physics blog post #1

    By bdavis,

    I am very interested in physics and in learning how different things work in the world around us. i class we learned the dot product and cross product and applied them briefly to kinematics in our first day of that unit. Although those are two very new concepts to me relating to vector math, i am interested in grasping the new concepts and applying them to my growing knowledge of physics.
    i wanted to take physics to gain more knowledge about what this area of science has to offer. i am very interested in sciences and i am planning on pursuing a career in medical research in the future.
    i hope to gain more knowledge about physics and being able to apply it to other areas of science to gain a better understanding of how things work.
    i am most excited to go more in depth in the material and better understand electrostatics and magnitism, my two most difficult units from last year.
    i am most anxious to get to apply the knowledge of kinematics to other areas of mechanics and learn more in-depth material.
    I anticipate learning a lot of new things and i am very excited.
  8. bdavis
    i have always been curious how it would be to drop an object from the top of the empire state building. It is obviously a long way down but exactly how fast would an object be traveling once it hit the ground? If i were to drop a golf ball for example, how fast would that travel? Well we can do this using my knowledge of one dimensional motion, a key physics concept. Acceleration due to gravity is -9.81 m/s for any object no matter the mass. Using our kinematic equations we can find out the final velocity any object will attain once it reaches the bottom of the Empire State building. The height of the empire state building is 443 meters tall. That will be our delta Y. Our acceleration is gravity which is -9.81 m/s. Our initial velocity is 0 m/s because we are dropping it from rest. We don't need the time in order to find the final velocity so we will use the equation Vf^2=Vo^2 + 2ay. That will be Vf^2=0 + 2(-9.8)(-443). Vf=93.18 m/s. That would be really fast and could seriously hurt someone. That is really cool!
  9. bdavis

    Shocking!

    By bdavis,

    Last year, i was blow-drying my little sister's hair and when i put the blow-dryer into the outlet, i got shocked. When i inserted the plug into the outlet, i accidentally put my finger too close to where the circuit was completed. I then realized that i completed a circuit when i plugged in the hair dryer. I did a little more research. I found out that the voltage of an outlet in a home is 120 Volts. Then i did research to find out the resistance in the blow-dryer. The blow-dryer i used had a resistance of 6 ohms. Using the equation I= (V/R) (I being the current, V being the voltage, and R being the resistance in Ohms), i found out that i was shocked with 20 amps of current. I went further to calculate that the Power generated in that circuit, from the equation P=(I*V) was 2400 W of power.
    Curcuits can be simple or complicated and they can generate a lot of current and power. I am glad that i wasn't hurt because if the voltage was greater and the resistance was smaller, i could have been in quite the predicament.
  10. bdavis

    Industrial catapults

    By bdavis,

    We recently built catapults as a project assigned by our physics teacher. Our goal for this project was to maximize the distance of the projectile, which in this case was a softball. We either had the choice of building a catapult or a trebuche but we decided to build a catapult. Using our knowledge of two dimensional motion, we set out to build a catapult that would launch the projectile at the optimal angle with the most applied force. We placed a wooden beam on our catapult at the spot that would cause our arm to release the catapult at 45 degrees, the optimal launch angle. We used garage springs to provide the force to the arm to accelerate the arm until it reached its launch point. We pulled the spring back to the base of the catapult, stretching it a good amount to provide a good source of tension in the spring. That force pulled the arm of our catapult up, launching our projectile at the optimal angle (45 degrees) so it could attain its maximum height and distance. Our catapult launched the softball a maximum distance of 35 yards which was a very solid result to a project that tested our knowledge on a very important physics concept. We were proud of ourselves.
  11. bdavis

    physics of a mowhawk!

    By bdavis,

    The varsity cross country team decided to get mowhawks to get pumped up for thier sectional race this past saturday. As a member of the cross country team i got one as well. Most of our runners had long enough hair to spike it and create very large and excentuated mowhawks. I didn't have enough hair to do that so i got the sides of my hair shaved off and my mowhawk looks like a drag strip right down the middle of my head. This type of mowhawk has some very unique properties. As a runner, i want to maximize my time. My type of mowhawk provides less air resistance that would be provided by my hair. With less hair on the sides of my head, the air can move past my head easier and the strip in the middle of my head can help to split the air on either side of my head. Therefore, when running, a mowhawk may look kind of dumb if the person can't pull it off but it can help improve a runners times on a day where head wind is a problem.
  12. bdavis

    Physics of a curveball!

    By bdavis,

    I am a man who loves baseball and when i figured out that physics plays a huge role in pitching, i got excited. Physics is exhibited very well in curveballs. A curveball is a pitch that was named for its movement; it curves on its path towards home plate as it reaches the batter.

    The pitcher grips the ball on the side just over one of the seems and when he throws it, he flicks his wrist hard creating the ball to spin sideways as it travels forward towards the plate. As it shows in the diagram, the rotation on the ball creates high pressure as the seems turn over which eventually makes it turn hard and dip towards the end of its flight. The harder it is thrown, the more dropping action it will experience because the greater the high pressure will be. Hitters better watch out because physics is not on their side when it comes to hitting a curveball.
  13. bdavis

    world series fun!

    By bdavis,

    So the world series for baseball happened not too long ago and something amazing happened. Hunter pence, an outfielder for the San Francisco Giants, broke his bat when swinging at a pitch but his bat hit the ball three times after he made initial contact.


    http://www.youtube.com/watch?v=mOkbQVsIk_0

    The ball made contact with the bat initially a few inches above the handle where he was holding it. In the video, you could see that the bat bent out as it was breaking and began to bend towards where the ball came off the bat. The bat and the ball collided in midair after initial contact and touched three times total. The physics involved with that is that the ball was traveling at such a high velocity and the bat was moving at a high velocity in the opposite direction, the bat couldn't withstand such a great force and it broke on contact. But the ball caused the bat to continue in its path towards the left where the ball was heading because it bent the bat on contact as it broke. Both objects were moving with the same speed coming off the bat and that is why they made contact a few more times. That doesn't happen often. The ball has to hit the right spot on the bat and the angle of trajectory of both the broken bat and the redirected ball have to be really close if not the same. If the bat was as light as the ball, they would have traveled together longer but the bat decelerated faster than the ball did due to higher air resistance caused by more surface to be exposed. Baseball has more physics involved than i realized!
  14. bdavis

    physics of body building!

    By bdavis,

    Many people might not think it but the meat-heads who body build conduct physics related actions everyday when they go to the gym. The weights they lift are objects that apply a force to the muscles that are targeted in different exercises. Newton's second law, net force= mass x acceleration (F=ma) shows that force is equal to the mass times the acceleration. So the weights that people lift when they work out have a mass that is accelerated by gravity to produce the force overcome by muscle movement. Building muscle mass can be attributed to Newtonian laws of Physics!
  15. bdavis
    One of the simplest baseball drills that only requires one person, a glove, a ball and a wall exhibits one of the basic yet essential physics concepts: Newtons third law. Newton's third law states that if something applies a force on an object, that object will apply a force of equal magnitude in the opposite direction.

    So when training for baseball, someone can throw a baseball against a wall with a certain force and the ball will come off the wall with the initial magnitude it first hit the wall with, but in the opposite direction. Newton's third law didn't take into account friction so the ball will be subjected to air resistance and won't make it back to the person with the same velocity but for the instances it strikes the wall and comes off the wall, air resistance is negligible. Therefore, Newton's third law can be observed.

  16. bdavis
    We are now entering our last quarter as seniors in high school. I want to rebound from an uncharacteristically bad academic performance in the third quarter and finish strong in the last quarter. This is now a prime time to start reviewing for the AP test that is looming in the very near future. I for one am quite a bit nervous but I have a plan to follow that will get me prepared for the day of the test:
    1. do 1 blog post a week
    2. Read text book a little bit each night
    3. do webassigns a little bit each night
    4. Read in my review book a little bit each night, reviewing previous units.
    5. get sleep
    6. eat a bagel with peanut butter everyday (got that one!)

    If I do this and take the initiative to begin studying now, I will be able to properly locate my weaknesses, other than the ones I already identified, and I will work to improve them for the day of the test. I will be prepared when I walk in there that fateful day in may. I guarantee i won't look like this:

    and if my pants are down, it will be out of my own accord!
  17. bdavis
    Ever since i saw my first Jackie chan movie (which i cannot remember off the top of my head), i have always been curious how a man, not especially strong and bulky with the muscles most football players possess, can break a cinder block in half with his bare hands. I previously thought that the cinder block would be too strong for even the most muscular man to even crack it let alone break it.



    In this video, the person had two thick bricks stacked on top of each other and he broke both of them simultaneously with his bare hand. He put the very edges of the bricks on blocks so they would provide a very minimal normal force in the opposite direction of the applied force of the karate chop. Also, he aimed at the middle of the block with his applied force to where the center of mass had the greatest force in the downward direction provided by gravity. Therefore, when the man made contact with the block, the block was subjected to the force of gravity down and the applied force of his chop. With no reinforcement below the middle of the block, the person applying the force will feel a minimal normal force applied by the block itself. A very large force must be applied by the person chopping at the block but with the assistance of gravity and no reinforcement under the block, breaking a brick with bare hands is easier than it appears to be!
  18. bdavis

    Centrifuges!

    By bdavis,

    I aspire to be involved in the medical field once i finish my schooling and one of the tools i hope to use is a centrifuge. Centrifuges are tools where test tubes are inserted into spaces around the outside of the tool. It then spins in a circle and the more it spins, the contents in the beakers are separated into their components. The contents in these beakers mostly consist of blood samples and organelles that need to be separated to be analyzed. Centrifuges use the centripital force to separate the components of the samples. The more massive objects/ components in the test tubes experience the greatest force due to the direct relationship between the force and the mass (F= (mv^2)/r). They will be pushed back to the bottom of the test tubes and the fluids along with the less massive components will be on top of the larger organells. When the spinning process of the centrifuge is complete, the smaller and larger components of the sample in the test tubes will be separated. The centripital force incorporated by the Centrifuge is very helpful in allowing medical researchers analyze smaller components of human blood.

  19. bdavis

    Circulatory system

    By bdavis,

    Our bodies conduct physics every second of everyday. Our bodies pump blood. Initially, one may think that the mere action of pumping blood has no correlation with physics at all. On the contrary, the blood in our bodies must be pumped through muscle contraction and applied force as well as pressure. Last year in physics B, we learned quite a bit about fluid mechanics and the relationship between force, pressure and area of the tube the fluids travel through. As our heart initially pumps blood from the heart, it travels through the arteries in the downward direction towards the lower part of our bodies. Not as much energy and force needs to be applied because gravity provides a lot of the force needed to carry the blood through the arteries through the body. That is why the arteries are larger and do not apply as much pressure and force as the veins do. Veins are the other muscular passage way that carries blood but it carries blood back to the heart to be replenished with oxygen. The veins need to carry the blood from the bottom of the human body, against the pull of gravity, towards the heart. Therefore, in order to successfully transfer the blood to the heart, a force greater in magnitude than the force of gravity needs to be applied. F=(P/A) This relationship shows that a smaller area will increase the applied force. The contractions of the veins provide the required pressure and the smaller radius of the veins compared to that of the arteries creates a greater force. That force overcomes the force of gravity so the blood can be constantly circulated within the human body.

  20. bdavis
    During the AFC football game yesterday night, the wind was blowing really strong from one end of the field to the other. That can be a good and a bad thing for the offenses on each team. The offense driving into the wind will have their quarterback's passes subjected to the wind and his passes won't travel as far. But for the quarterback and his offense traveling the other way, his passes will be thrown with the wind, thus making his passes travel farther with the wind carrying them to some degree. The wind alters the magnitude of the drag force that the air puts on objects in calm conditions. The drag force is given by the equation F= bv or F= cv where b and c are constants of different magnitudes. The wind increases the drag force for the balls thrown into the wind but it decreases the drag force for the balls thrown with the wind.
    Although one team may have had the advantage for part of the game, the Baltimore ravens won and that is all that matters. Harbaugh superbowl!
  21. bdavis

    Spitballin

    By bdavis,

    So when my family goes out to restaurants, my mom and i take the straws they give us, rip off the top part of the paper and shoot them at each other. We also make spitballs and fire them at each other at will before we receive our food. This relates to a lab we conducted in our Physics C class. We blew projectiles from straws and then blew those same projectiles through straws that are connected to other straws. Those projectiles traveled faster and farther. Velocity is calculated by dividing the displacement by the time the projectile traveled that certain distance. (V= (disp/time)) Also, the longer the straws were, the longer the constant force was applied to the projectile. The longer a force is applied on an object, the faster it will go and therefore the farther it will travel. That is how my mom and i make it interesting: we put many straws together to make the spitballs go faster at each other. Physics is clearly involved in even the most immature behaviors.

  22. bdavis

    The class so far

    By bdavis,

    So far for me, Physics C has been a challenge. There is a lot of information to learn and a lot of abstract ideas that I have difficulty wrapping my head around. Despite the many difficulties, that i know most of my fellow classmates are experiencing simultaneously, i find this class extremely rewarding. I have learned so much not only about physics but how to properly study and learn complex information accurately and effectively. I also find the content very interesting. So many things happen all around us everyday and i find it very interesting that we can find out how and why things happen. I am a very inquisitive person so i value this information. However frustrated i may get with the difficulties, i know that nothing in life that is worth learning comes easy and properly studying is a skill i will take with me through my travels to higher education. So i am excited to continue this course into the next semester.

  23. bdavis

    The class so far

    By bdavis,

    So far for me, Physics C has been a challenge. There is a lot of information to learn and a lot of abstract ideas that I have difficulty wrapping my head around. Despite the many difficulties, that i know most of my fellow classmates are experiencing simultaneously, i find this class extremely rewarding. I have learned so much not only about physics but how to properly study and learn complex information accurately and effectively. I also find the content very interesting. So many things happen all around us everyday and i find it very interesting that we can find out how and why things happen. I am a very inquisitive person so i value this information. However frustrated i may get with the difficulties, i know that nothing in life that is worth learning comes easy and properly studying is a skill i will take with me through my travels to higher education. So i am excited to continue this course into the next semester.

  24. bdavis

    My Third Quarter

    By bdavis,

    Well I started this third quarter off on a really bad foot when i got an atrocious test grade on the electric potential test. We followed that test with an independent unit in circuits and although my test grade in that unit wasn't anything special, it was a significant improvement. Then we got the magnetism independent unit. In AP-physics B, my understanding of the magnetism unit wasn't very strong but I felt like i had a better grasp of it by the end of last year. However, with an increase in difficulty of the problems and more complex concepts with magnetic monopoles, my mind was blown. I like the freedom we get with the independent units but with freedom comes great responsibility to get it done promptly. I envy my classmates who had took the initiative and got the unit done on time with a better understanding because that is what I should have done. Learning on my own, structuring my schedual, and managing my time is something I must improve as I move on towards higher education.
  25. bdavis
    Here are some of the necessary equations, values, and laws that one must memorize or quickly derive in order to achieve success on the AP-Physics C E & M exam:
    K=(1/(4(pi)(epsilon not)))
    F=(K(q1)(q2))/(r^2)
    E=F/q
    E=(Kq)/(r^2)
    E=(K/r^2)(integral from v to infinity of dq)
    Gauss's Law: Net flux= integral over the closed surface of EdA = Q/(epsilon not)
    V=w/q
    V=Kq/r
    e=1.6X10^-19 C
    a= (qE)/m
    Coulomb's Law:
    The force exerted by one point charge on another acts along the line between the charges. It varies inversely as the square of the distance separating the charges and is proportional to the product of the charges. The force is repulsive if the charges have the same sign and attractive if the charges have opposite signs.
    Rules for Electric Fields:
    1. Electric field lines begin on positive charges (or at infinity) and end on negative charges (or at infinity).
    2. The lines are drawn uniformly spaced entering or leaving an isolated point charge.
    3. The number of lines leaving a positive charge or entering a negative charge is proportional to the magnitude of the charge.
    4. The density of the lines (the number of lines per unit area perpendicular to the lines) at any point is proportional to the magnitude of the field at that point.
    5. At large distances from a system of charges with a net charge, the field lines are equally spaced and radial, as if they came from a single point charge equal to the net charge of the system.
    6. Field lines do not cross. (If two field lines crossed, that would indicate two directions for E at the point of intersection.)

    Depending on the conductor, if it is a shell, solid or hollow, different values of E will be obtained by the properties of the conductor and the radius given in the problem.

    That is the condensed version of the necessary things to know for electrostatics.

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