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bdavis

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Blog Entries posted by bdavis

  1. 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.

  2. physics of being a mechanic

    · bdavis · 12/31/2012 02:36 AM

    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.
  3. 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!

  4. Circulatory system

    · bdavis · 01/21/2013 08:41 PM

    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.

  5. Centrifuges!

    · bdavis · 01/21/2013 08:24 PM

    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.

  6. Physics of karate chopping!

    · bdavis · 12/26/2012 07:13 PM

    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!

  7. Skiing!

    · bdavis · 11/06/2012 12:43 AM

    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!

  8. Driving on the highway

    · bdavis · 11/06/2012 01:29 AM

    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.

  9. physics of body building!

    · bdavis · 11/06/2012 12:24 AM

    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!

  10. Physics of a curveball!

    · bdavis · 11/05/2012 10:15 PM

    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.

  11. Industrial catapults

    · bdavis · 11/05/2012 02:22 PM

    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.

  12. physics of a mowhawk!

    · bdavis · 11/05/2012 02:34 PM

    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.

  13. world series fun!

    · bdavis · 11/05/2012 10:37 PM

    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. Empire state building physics

    · bdavis · 11/05/2012 10:58 PM

    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!

  15. physics blog post #1

    · bdavis · 09/12/2012 03:07 AM

    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.

  16. Equation Dump for Magnetism!

    · bdavis · 04/01/2013 05:18 AM

    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.

  17. Opposites Attract ;)

    · bdavis · 03/30/2013 10:30 PM

    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!

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