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Relahi

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About Relahi

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  • Birthday 08/24/1995

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  1. Relahi

    Harmonics

    There is a trick guitar players use where they lightly tap a fret while plucking the string and making a high pitched noise. This is commonly called "playing harmonics". However even without any fancy tricks, a guitar player is playing harmonics. In order to understand this we need to know some basic physics on waves. When someone plucks the lowest string on a guitar, you hear an E. You may think you are hearing just that one sound, but really you are hearing multiple harmonics and overtones combining to make that note and pitch. The dominating sound is the fundamental, this is the pitch we can hear. A plucked guitar sting is a standing wave with two fixed points. The tension, density and length of the string all determine its note and pitch. waves travel slower on a more dense string and faster on a thinner string. This produces a lower pitch on the thicker strings and a higher pitch on the thinner ones. There are non-vibrating points on each string called nodes. a trick often used by guitar players is to lightly tap these nodes (found on the 5th, 7th, 12th and 19th frets), changing the length of the string and isolating one particular harmonic. This makes a high-pitched sound and raises the octave, depending on which harmonic is used. To isolate the first harmonic pluck the sting and simultaneously tap it at the 12th fret (it takes some practice). The wave is divided in half which doubles the frequency and the note is brought up one octave. This blocks the fundamental and makes the first harmonic dominate. This has to do with modifying the length of the sting, therefor changing its frequency, the speed of the wave and its pitch. The length of the sting (L) is equal to 1/2 of the wavelenght. L=1/2(wavelength). Blocking the string on the 7th or the 19th frets will divide the string into thirds. This time, both the fundamental and the first harmonic are blocked and the second harmonic dominates. This raises the note two octaves (L=2/2wavelength). The same thing occurs at the 5th and 24th frets but the string is divided into quarters, the fundamental, first and second nodes are blocked and the third harmonic dominates, raising the note three octaves (L=3/2wavelength). The attachment below is me playing the fundamental, first, second and third harmonics (respectively). video.wmv
  2. i never would have known how much physics was involved with kayaking!
  3. Kites are fun, but I have never thought about how they work from a physics perspective!
  4. How is it that when Micheal Phelps swims the butterfly he can glide effortlessly through the water and somehow resembles the mammal for which the stroke is named? Well it may not seem so, but Phelps is a physicist. He has perfected the stokes so that he is working with the laws of physics and mechanics, reducing drag, minimizing his surface area and maximizing his force against the water. The butterfly is arguably the most difficult swimming stroke. The swimmer throws both arms above his or her head and propells their body with a powerful dolphin kick. The main objective is to produce a lot of proplusive forces and reduce the resisitive forces. To reduce drag swmmiers wear hydrodunamic swimsuits, caps, and they even shave their body hair before big races. Another way swimmers resist drag is the streamline position. In streamline the swimmer's arms are up, their hands clasped tightly around their head, their legs are together and their toes pointed. It looks like this: This reduces the ammount of surface area on the body and therefor reduces the amount of drag. Swimming under water in streamline position with a dolphin kick is faster than swimming above the water because there is water for the body to push against verses if they were swimming above the water where there would be only ar to puch against. This brings us to the second goal in swimming which includes newton's third law: with every force there is an equal and oposite force. The amount of force the swimmer puts on the water with his or her hand or foot determines how far the stroke will take them. (F=ma). The mass of the person remains constant but when the force against the water increases, their accelleration also increases. Hand position is also a very important part of an efficient stroke. The ideal hand position is where the resultant of the lift and drag forces is opposite to the desired direction of movement. The swimmer the water backward at this angle, propelling them forward.
  5. The art of pottery requires a lot of patience, focus and a high tolerance for getting messy. Having a grasp on some basic physics concepts can also be a big help. The wheel spins as a result of centripetal acceleration. The diameter of the wheel and the velocity of the wheel (controlled by the potter) determine the wheel's centripetal acceleration (a=v2/r). The lump of clay is subject to centrifugal force (the tendency for an object to fly outwards on a circular path) because of the wheel's centripetal, or center seeking force. Thusm the clay's natural tenency is to fly off the wheel (not uncommon).The objective of the potter is to fight this force, manipulating the clay upward instead of outward. If we increase the velocity of the wheel, its centripetal force increases and requires the person to put more force on the clay with their hands in order to keep it from flinging off the wheel. The wheel spins faster around the outer edge than it does in the center. This is why one of the most important steps is to center the clay, making it less vulnerabel to the centrifugal force. Another force working against the clay is friction. The force of friction is dependent on the surface of the clay and the potter's hands ("mu" or the coefficient of friction) and the ammount of force placed on the clay by the person (N). Ff=muN When working with clay, a potter always as a bucket of water on hand to keep the clay wet especially during the initial centering process. The coeficent of friction is higher between dry clay and skin than it is between wet clay on skin. Because we must apply a high force on the clay (N) in order to shape it, we must counteract this force with a low coeffiecient of friction by keeping the clay wet and slippery. The key to successfully throwing a pot is to keep these forces in ballance. Apply too much external force and the clay will collapse. Allow friction and centrifugal force to take over too much and the piece will fly off the wheel.
  6. Relahi

    Physics of Music

    Its so cool that music follows so many principals of physics.
  7. Relahi

    Why the sky is blue

    It's interesting that the sky only appears blue to the observer because of optics.
  8. Relahi

    Double Rainbow!

    I'm sure we all remember the poplular Youtube hit where the hiker becomes completely overwhelmed with emotion at the sight of a "double rainbow all the way across the sky." So, maybe his reaction was slightly over dramatic, but the science behind the phenomenon is pretty exciting. Try to contain yourselves though. In order for a rainbow to form, there are a couplel conditions: there must be a lot of moisture in the air and the sun must be behind us. Sunlight is white and is made up of the combination of frequencies from the colors in the visible light spectrum . When the sunlight hits the droplets of water, they act as miniature prisms. The white light is refracted into the drop at the boundary between air and water. The difference in mediums and and the increase in the index of refraction causes the light to slow down and change direction. Then it is reflected off of the inside of the back of the drop and refracted once again as it exits the drop, this time being dispersed into the white light's components on the visible light spectrum: red, orange, yellow, green, blue and violet. The angle of reflection inside the drop is between 40 and 42 degrees. Although each individual drop disperses the entire visible light spectrum, the rainbow appears to be split into separate bands of color. This is because our eye percieves the drops that lie at a steeper angle to be red and the drops that lie at a less steep angle to be violet. Therefore, a rainbow appears differntly to different observers depending on their location. When the sun reaches an angle above 42 degrees in the sky, the rainbow will dissapear. A rainbow is not a fixed point or a tangible object, it is only the way our eye percieves refracted light at 40- 42 degrees. So what about the legendary double rainbow? A double rainbow is formed when the sunlight is reflected at two points on the inside of the raindrop instead of just one. This second reflection creates a secondary rainbow at an angle of 50-53 degrees, making it appear higher in the sky. The colors are in reverse order because the light is bent again as it leaves the raindrop. Circular rainbow?? Yes, rainbows are actually circular. From the ground we only see the top half of the circle because of the presence of the ground. If you were to see a rainbow from an airplane you may see the entire circle.
  9. Physics students in Mr. Fullerton's class conducted an experiment determine the acceleration due to gravity in a free falling object. The students ran through several trials utilizing a ball dropped from a controlled distance, 2 meters, and used a timing device to record the dropped ball's velocity. The students then calculated the average time, finding it to be .563 seconds. With this information in mind the studnets were able to calculate the acceleration due to gravity. Here is the table of variables the students utilized to find the acceleration: Vi = 0 m/s Vf = Not needed A = ? T= .563s By using the kinematic equation a=d/t, the students came to a final acceleration of 7.105 m/s^2. In comparision to the universally accepted value of 9.81m/s^2, the final acceleration was invalid due to a percent error of over 27%. Many variables can attribute to the large margin of error, including mechanical error in part due to the stopwatch.
  10. hi moose. yay cross country!
  11. Relahi

    Intro

    very cool that you like going on walks, they can be so relaxing and nice.
  12. Hi I'm Roxy and I'm a senior. I run cross country and do art (clay sculpture and pen are my favorites). This summer I took a nap almost every day, watched the first 5 seasons of The Office, and spent alot of my time lifegaurding here at the IHS pool. I like food and nice people and good music among other things obviously but those are the essentials. Honestly I'm not looking forward to senior year too much but am excited for what lies ahead after high school. I decided to take phyisics because I was told by many that it's an interesting class and is helpful when applying to college. Its good to get a basic understanding of all the sciences. I know absolutely nothing about physics except that making a tower out of spaghetti and getting it to support a marshmallow is really hard, so I'm excited to see what the class is about. It will be interesting to see how the world around us works.

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