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bdavis

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Blog Entries posted by bdavis

  1. bdavis

    Opposites Attract ;)

    By bdavis,

    In the dating world, people with opposite personality types seem to be attracted to each other. In the world of electrostatics and magnetism, opposite charges attract each other and opposite magnetic poles attract each other too. Particles with a positive charge, such as a positive test charge, are attracted to particles with a negative charge, such as a negative test charge. The particle with the greater magnitude of charge will attract the other with a greater force. For example, if a particle with positive charge has 2C of charge and a particle with negative charge has 1C of charge, then the particle with a postitive charge will exert a greater attractive force on the particle with negative charge than the attractive force the negative particle will exert on the positive particle. With magnets, the Northern end is attracted to the south end due to opposite magnetic poles. These properties play a very large role in understanding the subatomic relationships between particles of different charge and magnetic polarity in substances such as blood and water. These phenomena occur ever instantaneous moment of everyday!
  2. bdavis

    Dive Vs. Cannonball!

    By bdavis,

    What our dear friend charles merie eckert never mentioned in his series of swimming blog posts was the difference between a cannonball and an actual dive. When asked to visually show another person the difference between a cannonball and a dive, virtually anyone can demonstrate that. But when asked to explain what makes a cannon ball produce a bigger splash than a dive, few people can provide a sufficient response. The reason a cannonball produces a bigger splash than a dive is a greater amount of surface area of a person exposed when he/she hits the water. If the same person jumps off the board with an equal force and reaches the same height, that person will reach the surface of the water with the same acceleration and therefore the same force. But the cannonball causes that same force to be spread over a greater surface area. Therefore the greater amount of water affected by the force will exert an equal force, according to Newton's third law, which produces the splash. In a dive, that force is more concentrated over a smaller area therefore making the resulting splash smaller due to the smaller area affected by the applied force. Now Charles is going to say "well swimming and diving are two different things." He may be right in the technical sense but here we are physicists and that information provides no significant value to what i am explaining. So yes that is the technical explanation as to why a dive is different than a cannonball.
  3. bdavis
    du= -F(dl)
    dv=(du/q)
    dv=(-E)(dl)
    delta V= -integral (E)(dl)
    U=qV
    1eV=1.6X10^-19
    U=K(q1)(Q2)/r
    V=KQ/Square root((x^2) + a^2)) (V=0 at abs(X) = infinity
    For a spherical shell of charge:
    V= KQ/r, r>R (V=0 at r=infinity)
    V=KQ/R r
    For an infinite line charge V= 2k(lamda)ln(R_ref/R) for (V=0 at r=R_ref)
    Charge on a Nonspherical conductor:
    On a conductor of arbitraty shape, the surface charge density, (sigma), is greatest at points where the radius of curvature is smallest.
    Dielectric Breakdown:
    The amount of charge that can be placed on a conductor is limited by the fact that molecules of the surrounding medium undergo dielectric breakdown at very high electric fields, causing the medium to become a conductor.
    Dielectric Strength:
    The dielectric strength is the magnitude of the electric field at which dielectric breakdown occurs. The dielectric strength of air is E_max = 3 x 10^6 V/m = 3MV/m

    Not all of the equations are listed because some are required to be derived as parts on the AP test so by knowing the basic relationships and equations, deriving the rest of them become understandable and simple.
  4. bdavis

    The Cross Product

    By bdavis,

    At the beginning of the school year, we learned the two forms of vector multiplication: the dot product and the cross product. The more intricate of the two, the cross product, comes into play in many equations to provide very useful information. For example, in magnetism, F=I(BXL). This means the magnetic force is a vector cross product of the vector of the magnetic field crossed with the length of the object multiplied by the current flowing through that object. The resulting force will have values in the X, Y, and Z directions, indicating which plane the force is in relative to the length and the magnetic field. The Cross product is very helpful in revealing the direction and magnitude of the vector in that direction. It also helps to visualize where the other vectors (that influence the value of the resultant vector) are and what direction they are traveling in. Unlike most of my classmates, I like the cross product and although I don't have a firm understanding of it yet, I will continue to work on it so I can use it to better understand physics concepts as I take higher level physics courses.
  5. bdavis
    As a baseball player well below average height, I need to maximize every aspect of my game to be the best player I can possibly be. One aspect I have tirelessly worked on is my arm strength and throwing mechanics in order to maximize the velocity of throwing a baseball. Velocity is equal to displacement divided by time. Therefore, if there was more displacement over the same period of time, the velocity would be greater. I throw over the top which means that i have more of a windmill throwing motion rather than having a lower trajectory. There is virtually no time difference between the beginning of my throwing motion to when i release it at a 3/4 arm angle (a lower trajectory) or over the top. But by throwing over the top, my arm travels a little bit further and is therefore displaced more. If I apply that same force over the longer displacement during the same time span, then the resulting velocity of the ball when I release it will be greater from my over-the-top motion rather than a 3/4 motion. So I am trying to maximize every part of my game so I make the best of each day of baseball. So basically what I am saying is... come out to support the baseball team! The first game is home against Greece Athena at 4:30pm! Be there!

  6. bdavis
    F=qVXB
    F=ILXB
    Motion of Point Charges:
    A particle of mass m and charge q moving with speed v in a plane perpendicular to a uniform magnetic field moves in a circular orbit. The period and frequency of this circular motion are independent of the radius of the orbit and of the speed of the particle.
    Newton's 2nd law: qvB=m((v^2)/r)
    Cyclotron period: T= 2(pi)m/(qB)
    Cyclotron Frequency: f= 1/T = (qB)/(2(pi)m)
    Velocity Selector:
    consists of corssed electric and magnetic fields so that the electric and magnetic forces balance for a partivle moving with speed v.
    E=vB
    Mass Spectrometer:
    The mass-to-charge ratio of an ion of known speed can be determined by measuring the radius of the circular path taken by the ion in a known magnetic field.
    Magnetic dipole moment: u= NIAn
    Torque= t= u x B
    Potential energy of a magnetic dipole: U= -u . B
    Net force on a current loop in a uniform magnetic field is 0.
    Biot Savart Law:
    B= (u_0)Lxr/(4(pi)r^2)
    Magnetic field lines: the magnetic field is indicated by lines parallel to B at any point whose density is proportional to the magnitude of N. Magnetic lines do not begin or end at any point in space. Instead, they form continuous loops.
    Gauss's Law for magnetism: Net flux= integral over the closed surface( BdA)= 0
    Ampere's Law:
    Integral over the closed surface (B . dl)= (u_0)I_perm

    These are the main and basic laws and concepts of magnetism. Other equations can be derived for different objects with current flowing through them and deriving them helps to gain a better understanding of the relationships between different objects and their magnetic fields when current is induced.
  7. bdavis
    In both physics and chemistry, u, stands for a lot of things. u is the coefficient of friction, with subscripts indicating kinetic or static friction. It is the permeability of free space. It represents a magnetic moment. It indicates a micro unit (10^-6). It represents linear density. In chemistry, it represents velocity. u is also used to represent values in music, pharmaceutical sciences, computer science, software design, meat science and linguistics. Understanding each and every representation of u can be very difficult and many of the values produced do not require units so to an untrained eye, the value of u could mean many different things. Thus it could be interpreted in the wrong way. There are many other Greek letters that can be used to represent values in all fields of study so instead of overusing u, other unused Greek letters should be incorporated. As a student who has to discern between five different representations of u, it becomes difficult at times if the topic at hand isn't 100% clear. So i believe u shouldn't be used as much and other Greek symbols should be incorporated into these diverse fields of study.
  8. bdavis
    In preparation for the AP Physcis-C exam, I did a number of things that helped me to properly review the year's material.

    1.) I looked over each test and studied the questions that gave me the most trouble.

    2.) I re-read the parts of the text book that described specific properties regarding certain topics during the year such as the properties specific to conducting and non-conducting shells. Also, I looked up and reviewed kirchoff's loop rules and the properties that go along with the circuits in which those rules apply.

    3.) I wrote all of the equations down on separate sheets of paper, one for mechanics and the other for electrostatics and magnetism. And the more i wrote them, the better I recognized them when the day of the AP came.

    4.) I did a little each day and didn't stress myself out too much which helped me to go into the test confident and calm. I set myself up to think effectively and critically for however long we were given for the tests.

    I felt the way I prepared myself for the test was well thought out and it worked pretty well. I probably could have studied the multiple rules and properties better but in the future I know what methods of studying work for me: repetition is the key to my success.
  9. bdavis
    On may 13th 2013 I sat down in my high school in the afternoon for my AP Physcis C exam. The first test I had to take was the mechanics exam: 45 minutes for the multiple choice and 45 minutes for the free response questions. The 35 question multiple choice part of the exam wasn't all that difficult but a bunch of problems took a long time to figure out. I didn't finish that part of the exam so I had to guess on the last 4 questions. The beginning of the free response section began with a air resistance question. The week before, my physics teacher suggested we review how to do air resistance because he thought there might be one question on the test where we would need that information. I didn't heed his warnings and advice so I didn't review it as much as I should have. I was able to answer most of the question but not to the extent I would have hoped to. The last two problems were very do-able and I was able to finish the mechanics free response questions.

    The electrostatics and magnetism section of the exam was a bit more difficult in my opinion. The multiple choice section required a lot of work to be calculated and figured out by hand so again, I wasn't fortunate enough to finish: I had to guess on the last 5 questions. The free response questions only got worse. The first and third free response questions were do-able and I thought I did very well overall on those two but the second one was nearly impossible beyond the second part of that question. I finished most of that part but there were definitely some aspects I didn't understand as well as I probably should have.

    The Physcis C AP was very difficult and I am very nervous in anticipation to see what my scores are.
  10. bdavis
    Rocket flight is much more difficult and requires much more calculation than it may seem to those not involved in NASA. The more fuel a rocket may have and the more powerful the engine a rocket may have doesn’t always mean it will travel the fastest or the farthest. The heavier the fuel tank, the more the rocket is affected by the pull of the planet’s gravity. Also, the more massive the rocket is, the more it is affected by the air resistance of the planet’s atmosphere. Many calculations go into finding the optimal shape and form for a rocket before constructing it. Rockets cost millions of dollars to construct and they better be able to achieve the intended mission. Also, nose cones and wings are applied to decrease the air resistance on the rocket, making it more aerodynamic.


  11. bdavis
    Rocket flight is much more difficult and requires much more calculation than it may seem to those not involved in NASA. The more fuel a rocket may have and the more powerful the engine a rocket may have doesn’t always mean it will travel the fastest or the farthest. The heavier the fuel tank, the more the rocket is affected by the pull of the planet’s gravity. Also, the more massive the rocket is, the more it is affected by the air resistance of the planet’s atmosphere. Many calculations go into finding the optimal shape and form for a rocket before constructing it. Rockets cost millions of dollars to construct and they better be able to achieve the intended mission. Also, nose cones and wings are applied to decrease the air resistance on the rocket, making it more aerodynamic.


  12. bdavis

    momentum headaches!

    By bdavis,

    In my soccer game yesterday, I experienced quite a collision. Not with anyone person. I collided with the ball. In soccer, each player is allowed only to use their feet, their body and their head, not their arms or hands. Hands and arms may not come in contact with the ball. Yesterday, I had a few head balls that demonstrate the concept of conservation of momentum. A teammate of mine kicked the ball from the sideline and I redirected it with my head towards the goal. The glancing blow off of my head sent the ball in one direction while my head recoiled and traveled in another. My head, being more massive than the ball, moved only slightly in the opposite direction while the ball flew a good 30 feet to my left. Now, momentum works at angles and the trajectory of the ball was at an angle so its path changed at another angle. My head isn’t a perfectly round surface so the balls new trajectory couldn’t be easily calculated by a normal physics c student, at least without more given information about the dimensions of my head. Needless to say, I left the game with quite a headache.
  13. bdavis
    After we took the AP physics C test, we began to experiment with a computer game known as the Kerbal Space Program. In this game, creatures called Kerbals inhabit a planet named Kerbin (surprisingly similar to Earth) and we had to fulfill many missions related to space travel. I really enjoy the Kerbal space program because at the same time it is a fun experience and it incorporates a lot of physics topics such as the incorporation of gravity and air resistance. It also introduces Orbital movement and space flight. I really enjoy the Kerbal Space Program.

    Also, I found the tutorials on YouTube very helpful in understanding how enact a lot of the maneuvers.




  14. bdavis
    In light of the end of school, I want to review how my 4th quarter has been. My third quarter was slightly less than stellar taking into account my previous accomplishments and I feel like that was the “swift kick in the a**” that I needed to get right back on track. From then on in the 4th quarter, I turned things around, studied hard for my AP classes and did well on my exams. After that I focused on my other non- AP classes and increased my grades considerably. In physics, we started the Kerbal Space Program and that was a lot of fun but at the same time it was educational. We got to learn about the physics of flying a rocket and how to manage a business through our online write-ups. My partner Zach did most of the work because he thoroughly enjoyed it but I forced my way through in the end so I could get a taste of that experience. I will always regret doing these blogs late because that wasn’t fair to my family or my physics C teacher who was kind enough to accept them. Overall I feel like the 4th quarter went well but I still have some work to do before college.
  15. bdavis
    Now it may seem like I am running out of ideas but planting a flower incorporates an important physics concept. When removing a flower from its packaging, a proper amount of force must be applied. If too much force is applied when removing a flower from its packaging, then it will therefore accelerate too much and the roots at the bottom of the package will separate, killing the innocent flower. When actually planting the flower, after digging an appropriate sized hole, you don’t need to shove it into the ground. By gently placing the flower into the subsequent hole and covering the surface with dirt is the first step to execute. Secondly, a firm yet gentle pressure must be applied to pack the soil down on top of the flower so the roots and stem are secured. If too much pressure is applied on such a small area, it will experience a greater force, thus accelerating into the ground more and crushing the roots. The stem will therefore become unstable and fall over. The flower will then shrivel up shortly after. In gardening, a lot of finesse is required so as to not kill the flowers. These two equations (force equals pressure times area and net force equals mass times acceleration) show how and why too much applied will harm the flower.
  16. bdavis
    Yesterday in class we learned about Einstien’s theory of relativity and time travel. Our physics teacher explained to us how traveling in space or being on another planet can alter the amount of time you feel and your body experiences. If someone is in Space for 70 earth years, their body doesn’t age those 70 earth years if they are far enough away from the Earth’s atomsphere. We also learned about how the speed of light is the fastest speed that can be achieved in the universe: 2.998 x 108 m/s. We discussed how no object in the universe can attain that speed because as an object moves faster, it gains mass. The more mass it gains, more force is needed to accelerate the mass to continue increasing its velocity. No matter how small the initial mass is, it will become so big that there is not enough energy in the universe to apply a force strong enough to accelerate it to the speed of light. Furthermore, we also learned about how string theory applies with electron transfer. In theory, two electrons next to each other are connected by a “string” and they have opposing spins because no two electrons can spin in the same direction when they are next to each other. When one flips, the second one is supposed to instantaneously flip as well to maintain the different directions they spin in. It has only been proven to be true at a maximum of 13 miles across a river in Russia but physicists are still working on it. I find this concept fascinating and I really would like to know more about it.
  17. bdavis

    "Tag"

    By bdavis,

    We just recently finished a game in calculus. We called the game “tag” but it really was a game of assassin where we could get people out by shooting them with water guns. We had to be very stealthy because no one was supposed to know about it. To keep up with the stealthy behavior, shooting long range squirt guns would have been really effective to get people out without them realizing what hit them. In the beginning of the year we conducted a lab with q-tips and plastic straws. That lab demonstrated the concept of velocity and the relationship between displacement and acceleration. If we had water guns that had a longer nozzle with triggering mechanisms that would apply a constant force on the water from the beginning to the end of the nozzle, then the water would be accelerated over a longer displacement. F=ma and the longer an object is accelerated, the greater its velocity. Water guns with longer nozzles would be able to shoot water out faster and over longer distances if shot with an angle of appropriate trajectory. If they weren’t that noticeable, then it could have worked to our advantage. The best assassins have a good understanding of basic physics.

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