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AliciaDAnnunzio

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  1. AliciaDAnnunzio

    Singing bowls

    By AliciaDAnnunzio,

    Tibetan singing bowls are similar to humming crystal glasses. A mallet is used to vibrate the metal bowl by sliding along the edge in a circular motion. This creates a standing wave. The bowl acts as a resonating chamber, each edges' wave reflects off of the opposite side; which gives it it's unique sound. If the person controlling the vibrations does it gently enough and at the correct speed, the frequency remains constant while the amplitude will most likely increase. An increase in the speed of these pulses can create an increase in frequency and vise-versa. A difference in the medium, such as having a different size or kind of metal, can also affect the pitch of its hum. This is how Tibetan singing bowls work.
  2. AliciaDAnnunzio
    There are four main forces acting upon a plane which controls the way it flies. Lift is when is moves upward, as opposed to the gravity which pulls it downward. Thrust is when is moves in a forward direction, which acts against the force of drag (which is when air resistance pulls it backward.) In order for a plane to become airborne, its force of life must be greater than the force of gravity (9 m/s^2 on Earth.) Also, the propellers must thrust it in the direction it wants to go with a greater force than that of air resistance. This is how a plane flies.
  3. AliciaDAnnunzio
    With my chorus concert tonight, it was brought to my attention (by Mr. Fullerton) that there is, of course, physics involved in how sound is amplified at concerts. Behind the musicians at a concert, there is a sound shell. Why is it there? It helps amplify the music for the audience. This works by acting as a barrier for the sound waves. The sounds waves travel in all directions, including towards the sound shell, and is reflected towards the musicians and the audience. This not only allows the musicians to hear themselves better, but it helps the crowd enjoy the beautiful music coming from the stage.
  4. AliciaDAnnunzio
    When one plays a guitar, they are pressing down on the strings. Pressing down on different places on the string causes changes in tension, therefore changing the medium. When the medium is changed and you pluck the string, thereby creating a pulse, there is a change in frequency. The change in the frequency of the wave is what causes the string's audible change in pitch.
    Depending on the pattern of the pulses and the frequency of the string, the string becomes a standing wave. When the natural frequency of the material is mimicked by a separate wave brought into contact with this material, it begins to vibrate. This concept of resonance can be exemplified by a 12-string guitar. For every one note on a 6-string guitar (E, A, D, G, B, e) the 12-string guitar has two, in varying octaves. Because each pair of strings has the same note but in different octaves, the natural frequency of the similar mediums are mimicking each other when played together. When one pair of strings is played at the same time, the waves bounce off each other, causing the strings to vibrate, much more than possible on a 6-string guitar. This is what gives 12-string guitars that unforgettable sound.
  5. AliciaDAnnunzio
    The speed of a wave depends solely on the medium. It is common knowledge that sound travels faster underwater than through air; but, contrary to what logic tells us, sound also travels faster through salt water than through fresh water. Usually, the rule of thumb is that sound travels slower in a denser medium of the same phase. But why would sound travel faster in salt water if it is denser?
    It's because of the difference in bulk modulus. "The bulk modulus of a substance measures the substance's resistance to uniform compression. It is defined as the ratio of the infinitesimal pressure increase to the resulting relative decrease of the volume." So basically bulk modulus is the measure of how hard it is to compress a substance.
    The speed of sound decreases in water with increased density, but increases in water with increasing bulk modulus. Therefore, because salt water is more resistant to compression, sound travels through it faster.
  6. AliciaDAnnunzio
    In a thunder storm, lightning always comes first, because the speed of light is faster than the speed of sound. There's a trick commonly used to find how far away you are from the lightning during a storm. When you see the flash of lightning, you begin to count. You continue counting and stop when you hear the thunder. Let's say you count to ten. Then you are supposedly ten miles away from the lightning. The common misconception is that each second represents one mile of distance between you and the storm. According to the National Lightning Safety Institute, "Light from lightning travels at the speed of 186,000 miles per second (300,000 km/second), arriving at the observer in about 10 microseconds when the strike point is 1.85 miles (3 km) away. The sound wave, at an air temperature of 68° F (20° C) and atmospheric pressure of 29.92 in of mercury or 1,013.25 millibars, arrives more slowly in about 10 seconds." In this scenario of common storm conditions, every five seconds represents 1 mile of distance between you and the storm. Looks like we were closer to getting struck than we thought we were!
  7. AliciaDAnnunzio
    The Doppler Effect is the change in wave length caused by motion. The classic example is the sirens on fire trucks and ambulances. The Doppler Effect is responsible for the change in the pitch of the siren as it speeds by. The way it works is the sirens are producing sound waves. When the truck moves, the distance between the waves is reduced, causing them to "bunch together" and travel at a higher frequency.

    This concept can also be applied to water. The current in a pool or a pond usually travels at a steady rate. But when someone adds motion to this current, it causes the waves to move faster and closer together than they normally would. This is what causes the rings seen when energy is added to the water. The faster the motion, the closer together these waves become.
  8. AliciaDAnnunzio
    No one can deny the awe felt when seeing a rainbow. The refraction of white light through prisms is a fascinating topic. It's easy to understand that light can be separated into the six colors of rainbow-red, orange, yellow, green, blue, and purple. But how exactly does it work?
    When light is shined through a prism, the energy of the light is absorbed by the atoms of the material. If the frequency of the light wave doesn't match the frequency of the vibrating electrons, the energy is reemitted by the atom. The light wave then travels through the "interatomic vacuum" and into the next atom in the material. This disturbance in the energy of the atoms causes the different frequencies of each color of light to separate and disperse in all different directions. The minuscule water droplets in clouds act as tiny prisms, and in the right conditions, refract sunlight. All of these tiny prisms are what cause the rainbows we see in the sky!
  9. AliciaDAnnunzio
    Anyone who has experience with tuning string instruments understands the concept of the Law of Sympathetic Resonance. Wikipedia explains it like this: "Sympathetic resonance or sympathetic vibration is a harmonic phenomenon wherein a formerly passive string or vibratory body responds to external vibrations to which it has a harmonic likeness." To put it in simpler terms, it's when two tones are played at the same time and one can hear the sound waves beating off of each other. The smaller the interval between the two notes, the faster the waves beat against each other. For instance, let's say you want to tune the A string on a guitar. You could play an A on the E string, then pluck the untuned A string and let the two waves collide and bounce off each other. In order to tune the string, you listen to this resonance and slowly turn the tuning peg until the two tones become one note, and are therefore in unison. This is how you can use sound frequencies in order to perfect the sound of an instrument.
  10. AliciaDAnnunzio
    While learning about orbits in physics, we were told that, "a force, such as gravity, pulls an object into a curved path as it attempts to fly off in a straight line." I'll use Newton's analogy for further elaboration: let's say a canon were to be fired off the top of a very tall mountain. Since projectiles have a parabolic trajectory, the cannonball would go up, stop briefly, then come back down. But, depending on the velocity at which it is fired, the cannonball would go up, and try to come back down; but since it has been fired so far away from the Earth, the ground would curve away from the ball. Therefore, the Earth's gravity would keep the cannonball in a perpetual state of "coming back down." In application to Earth, since the moon is constantly in a state of "coming back down," it is VERY slowly getting closer to the Earth...at least that's what we learned in class. (Some studies say otherwise.) I was wondering if this concept applies to the Earth's orbit around the sun. If so, could this possibly be an explanation for climate change?

    Obviously there are flaws with this theory. The rate at which our environment is changing is accelerating much too quickly for our Earth's orbit to be the direct cause. But is it a contributing factor? According to studies published on physicsworld.com, "the Earth could be closer than previously thought to the inner edge of the Sun's habitable zone." This could mean that as the amount of CO2 increases in Earth's atmosphere, and as the Earth continues to orbit the sun year after year; the air's capacity to hold water vapor will increase as well. Water vapor also tends to act as a greenhouse gas in our atmosphere. As a result, the global average temperature will rise, and it has been theorized that the oceans would begin to evaporate. Our current average global temperature is 288 K; but according to Ravi Kopparapu at Penn State, if we continue burning this amount of fossil fuels in the future, our atmosphere could reach a catastrophic 340 K by the year 2100. Other studies don't foresee global temperature this high until the year 2300, but it is definitely rising.

    So it turns out our orbit around the sun is a contributing factor in climate change.

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