Sounds

Definition Sounds

Sound is one of a wave, the longitudinal wave. Longitudinal waves are waves that the direction parallel or coincide with the direction of vibration. Examples of longitudinal waves are waves and slinki waves sound in air.

The sound of the waves has the same properties with the properties of waves, namely:

a. Can be reflected (reflection)

The sound can occur when sound is reflected on the surface of a hard object, such as the surface of the stone wall, cement, steel, glass and zinc.

Example: 

• Our voices are louder in the cave due to the reflection of sound from the walls of the cave. 
• Our voices inside the building or music studio that does not use a silencer.

b. Can be refracted

Reflected is bending toward trajectory wave after passing through the boundary between two different media.

Example: At night the sound of thunder sounded louder than during the day because of the refraction of sound waves.

c. Can be combined (interference)

As well as the interference of light, sound interference also requires two coherent sources of sound.

Example: Two loudspeakers are connected to a signal generator (audio frequency generator tool) can function as two coherent sources of sound.

d. Can be bent (diffracted)

Diffraction is flexing incident sound wave when it passes through a narrow slit.
Example: We can hear the voices of different people and covered all subjects, as the sound passes through narrow slits that are passable sound.

The sound occurs when there are three conditions as follows.

1. The sound source

    Objects that can generate sound called sound source. Examples of sound sources is a variety of musical instruments, such as guitar, violin, piano, drums, trumpet and flute.

2. Substance Intermediaries (Medium)

     Sound waves are longitudinal waves that do not appear. The sound can only propagate through the medium of an intermediary. For example air, water, and wood. Without an intermediary medium sound can’t propagate so it will not be heard. Based on research, a solid sound propagation medium is best compared to liquids and gases. 

3. Listener
The sound can be heard when there are listeners. Human auditory equipped, ie the ear hearing aids.

The vibrations emanating from objects that vibrate, up to our ears in general through the air in the form of waves. Because the waves can be in the air only longitudinal waves, the sound propagates through the air is always in the form of longitudinal waves. We need to remember that it is sealing and longitudinal waves can propagate through extensional three states of matter are: solid state, liquid and gas.

 There are three aspects of sound as follows:

a. The sound produced by a source such as another wave, the sound source is vibrating body.

b. Transferred energy and sound sources in the form of longitudinal waves.

c. The sound is detected (known) or an instrument by ear wave propagation speed of sound in air is affected by the temperature and density of matter trajectory

Based on the frequency, the sound can be classified into three. There are as follows.

1. Infrasound, sound whose frequency is below 20 Hz.

2. Audiosonik, is a sound frequency between 20-20000 Hz.

3. Ultrasonic, is the sound frequency above 20,000 Hz.

The human ear has a hearing limit. Sound that can be heard is the sound man with a frequency of 20 Hz to 20,000 Hz, which is audiosonik. Infrasound and ultrasound can’t be heard by humans. Infrasound can be heard dogs, crickets, geese, and horses. Ultrasound can be heard by bats and dolphins.

Sound Reflection

The sound will be reflected if the surface of a hard object, such as a stone wall or a surface of cement, steel, glass, and zinc. In contrast, most of the sound will be absorbed if the surface is soft objects, such as cloth, rubber, foam, cork, rugs, and wool (silencer objects). If we say a few words then a few syllables or words between the sound comes with reflected sound mutually destructive, so that we only share a single audible to the last syllable of the reflected sound. This event is called reverberation or boom. In a confined space such as a cinema, concert hall music, to reduce echo, wall and ceiling mounted silencer.

Sound Reflection Law

The following two laws of reflection of light are applicable to sound waves as well

1. The incident wave, the normal to the reflecting surface and the reflected wave at the point of incidence lie in the same plane.

2. The angle of incidence ∠i is equal to the angle of reflection ∠r.  

Kinds of Sound Reflection

Reflected sound can be divided into 3 kinds. There are as follows.

1. Strengthen the reflected sound is reflected sound original sound that can amplify the original sound. It usually occurs in circumstances between the sound source and the reflective wall is not so far away (less than 10 meters)

2. The boom is reflected sound that sounded almost simultaneously with the original sound. Usually occurs at a distance of between 10 to 20 meters.

3. The echo is reflected sound is heard after the original sound. Usually occurs at a distance of more than 20 meters.

Application of Sounds Reflection

1. Detecting Defects and Cracks on Metal

    To detect cracks in metal or concrete structures used ultrasonic scanning were used to check for hidden cracks on parts of the aircraft, which later could endanger aircraft flight. In a routine examination, vital parts of the in-plane ultrasonic scanning manner. If there are cracks in the metal, ultrasonic reflections from cracks will be detected. Cracks are then examined and addressed immediately before the aircraft allowed flying.

2. Measure the depth of the sea 

    By using SONAR we can measure the depth of the sea. At the bottom of the vessel wall is installed a vibration source (oscillator). Mounted near the receiver oscillator vibrations (hydrophone). If the transmit pulse takes a long time to get back to the receiver,  in and vice versa. If the time of vibration (sound) propagating (t) for a distance second commute is 2 L meters, the propagation speed can be calculated as follows.

V = 2L / T or 2L = v x t or L = v x t / 2

Where:

v = propagation speed of sound (m / s)

L = inside the sea (m)

t = time (t)

3. Knowing the position of submarines by sending ultrasonic waves from the boat to the underwater hunter.

4. Knowing the position of schools of fish in the sea.

5. Knowing the pockets of petroleum basins by sending sound waves into the    ground.

6. The Use in Medical 

     Examination to see inside the human body using ultrasonic pulses is called ultrasound (ultrasonography).  In the human body, ultrasonic pulses are reflected by the tissues, bones and body fluids with different density. Reflecting ultrasonic pulses emitted Ulsa can produce images of body parts that were found by the ultrasonic pulses on the oscilloscope screen.

Ultrasound is particularly useful in medical diagnosis since some of the following.

• Ultrasonic much safer than X - rays that can damage the cells of the human body due to ionization, it is safer to use ultrasound to view the fetus in the mother's stomach than light - X. 
• Ultrasonic can used continuously transform and see the movement of the fetus or lever one, without injuring or pose a risk to patients. 
• Ultrasound can measure the depth of an object under the skin's surface, while the resulting image rays - X is flat with no clue about the depth. 
• Ultrasound can detect differences in the tissues in the body that can’t be done-ray - X. This ultrasonic sometimes able to find tumors or clots in the human body.

Resonance

In sound applications, a resonant frequency is a natural frequency of vibration determined by the physical parameters of the vibrating object. This same basic idea of physically determined natural frequencies applies throughout physics in mechanics, electricity and magnetism, and even throughout the realm of modern physics. Some of the implications of resonant frequencies are:

1. It is easy to get an object to vibrate at its resonant frequencies, hard to get it to vibrate at other frequencies.

2. A vibrating object will pick out its resonant frequencies from a complex excitation and vibrate at those frequencies, essentially "filtering out" other frequencies present in the excitation.

3. Most vibrating objects have multiple resonant frequencies.

Resonance and Musical Instruments

Musical instruments produce their selected sounds in the same manner. Brass instruments typically consist of a mouthpiece attached to a long tube filled with air. The tube is often curled in order to reduce the size of the instrument. The metal tube merely serves as a container for a column of air. It is the vibrations of this column that produces the sounds that we hear. The length of the vibrating air column inside the tube can be adjusted either by sliding the tube to increase and decrease its length or by opening and closing holes located along the tube in order to control where the air enters and exits the tube. Brass instruments involve the blowing of air into a mouthpiece. The vibrations of the lips against the mouthpiece produce a range of frequencies. One of the frequencies in the range of frequencies matches one of the natural frequencies of the air column inside of the brass instrument. This forces the air inside of the column into resonance vibrations. The result of resonance is always a big vibration - that is, a loud sound.

Woodwind instruments operate in a similar manner. Only, the source of vibrations is not the lips of the musician against a mouthpiece, but rather the vibration of a reed or wooden strip. The operation of a woodwind instrument is often modeled in a Physics class using a plastic straw. The ends of the straw are cut with a scissors, forming a tapered reed. When air is blown through the reed, the reed vibrates producing turbulence with a range of vibrational frequencies. When the frequency of vibration of the reed matches the frequency of vibration of the air column in the straw, resonance occurs. And once more, the result of resonance is a big vibration - the reed and air column sound out together to produce a loud sound. As if this weren't silly enough, the length of the straw is typically shortened by cutting small pieces off its opposite end. As the straw (and the air column that it contained) is shortened, the wavelength decreases and the frequency was increases. Higher and higher pitches are observed as the straw is shortened. Woodwind instruments produce their sounds in a manner similar to the straw demonstration. A vibrating reed forces an air column to vibrate at one of its natural frequencies. Only for wind instruments, the length of the air column is controlled by opening and closing holes within the metal tube (since the tubes are a little difficult to cut and a too expensive to replace every time they are cut).

Read More

Digestive System

DIGESTIVE SYSTEM

DEFINITION

The digestive system is made up of the gastrointestinal (GI) tract—also called the digestive tract—and the liver, pancreas, and gallbladder. The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. The hollow organs that make up the GI tract are the mouth, esophagus, stomach, small intestine, large intestine—which includes the rectum—and anus. Food enters the mouth and passes to the anus through the hollow organs of the GI tract. The liver, pancreas, and gallbladder are the solid organs of the digestive system. The digestive system helps the body digest food.

Bacteria in the GI tract, also called gut flora or microbiome, help with digestion. Parts of the nervous and circulatory systems also play roles in the digestive process. Together, a combination of nerves, hormones, bacteria, blood, and the organs of the digestive system completes the complex task of digesting the foods and liquids a person consumes each day.

THE IMPORTANCE

Digestion is important for breaking down food into nutrients, which the body uses for energy, growth, and cell repair. Food and drink must be changed into smaller molecules of nutrients before the blood absorbs them and carries them to cells throughout the body. The body breaks down nutrients from food and drink into carbohydrates, protein, fats, and vitamins.

Carbohydrates. Carbohydrates are the sugars, starches, and fiber found in many foods. Carbohydrates are called simple or complex, depending on their chemical structure. Simple carbohydrates include sugars found naturally in foods such as fruits, vegetables, milk, and milk products, as well as sugars added during food processing. Complex carbohydrates are starches and fiber found in whole-grain breads and cereals, starchy vegetables, and legumes. The Dietary Guidelines for Americans, 2010, recommends that 45 to 65 percent of total daily calories come from carbohydrates.

Protein. Foods such as meat, eggs, and beans consist of large molecules of protein that the body digests into smaller molecules called amino acids. The body absorbs amino acids through the small intestine into the blood, which then carries them throughout the body. The Dietary Guidelines for Americans, 2010, recommends that 10 to 35 percent of total daily calories come from protein.

Fats. Fat molecules are a rich source of energy for the body and help the body absorb vitamins. Oils, such as corn, canola, olive, safflower, soybean, and sunflower, are examples of healthy fats. Butter, shortening, and snack foods are examples of less healthy fats. During digestion, the body breaks down fat molecules into fatty acids and glycerol. The Dietary Guidelines for Americans, 2010, recommends that 20 to 35 percent of total daily calories come from fat.

Vitamins. Scientists classify vitamins by the fluid in which they dissolve. Water-soluble vitamins include all the B vitamins and vitamin C. Fat-soluble vitamins include vitamins A, D, E, and K. Each vitamin has a different role in the body’s growth and health. The body stores fat-soluble vitamins in the liver and fatty tissues, whereas the body does not easily store water-soluble vitamins and flushes out the extra in the urine.

THE DIGESTIVE PROCESS

Digestion works by moving food through the GI tract. Digestion begins in the mouth with chewing and ends in the small intestine. As food passes through the GI tract, it mixes with digestive juices, causing large molecules of food to break down into smaller molecules. The body then absorbs these smaller molecules through the walls of the small intestine into the bloodstream, which delivers them to the rest of the body. Waste products of digestion pass through the large intestine and out of the body as a solid matter called stool.

Table 1 shows the parts of the digestive process performed by each digestive organ, including movement of food, type of digestive juice used, and food particles broken down by that organ.

Table 1. The digestive process

Organ	Movement	Digestive Juices Used	Food Particles Broken Down
Mouth	Chewing	Saliva	Starches
Esophagus	Swallowing	None	None
Stomach	Upper muscle in stomach relaxes to let food enter and lower muscle mixes food with digestive juice	Stomach acid	Protein
Small intestine	Peristalsis	Small intestine digestive juice	Starches, protein, and carbohydrates
Pancreas	None	Pancreatic juice	Starches, fats, and protein
Liver	None	Bile acids	Fats

The large, hollow organs of the GI tract contain a layer of muscle that enables their walls to move. The movement of organ walls—called peristalsis—propels food and liquid through the GI tract and mixes the contents within each organ. Peristalsis looks like an ocean wave traveling through the muscle as it contracts and relaxes.

Esophagus. When a person swallows, food pushes into the esophagus, the muscular tube that carries food and liquids from the mouth to the stomach. Once swallowing begins, it becomes involuntary and proceeds under the control of the esophagus and brain. The lower esophageal sphincter, a ringlike muscle at the junction of the esophagus and stomach, controls the passage of food and liquid between the esophagus and stomach. As food approaches the closed sphincter, the muscle relaxes and lets food pass through to the stomach.

Stomach. The stomach stores swallowed food and liquid, mixes the food and liquid with digestive juice it produces, and slowly empties its contents, called chyme, into the small intestine. The muscle of the upper part of the stomach relaxes to accept large volumes of swallowed material from the esophagus. The muscle of the lower part of the stomach mixes the food and liquid with digestive juice.

Small intestine. The muscles of the small intestine mix food with digestive juices from the pancreas, liver, and intestine and push the mixture forward to help with further digestion. The walls of the small intestine absorb the digested nutrients into the bloodstream. The blood delivers the nutrients to the rest of the body.

Large intestine. The waste products of the digestive process include undigested parts of food and older cells from the GI tract lining. Muscles push these waste products into the large intestine. The large intestine absorbs water and any remaining nutrients and changes the waste from liquid into stool. The rectum stores stool until it pushes stool out of the body during a bowel movement.

Digestive juices contain enzymes—substances that speed up chemical reactions in the body—that break food down into different nutrients.

Salivary glands. Saliva produced by the salivary glands moistens food so it moves more easily through the esophagus into the stomach. Saliva also contains an enzyme that begins to break down the starches from food.

Glands in the stomach lining. The glands in the stomach lining produce stomach acid and an enzyme that digests protein.

Pancreas. The pancreas produces a juice containing several enzymes that break down carbohydrates, fats, and proteins in food. The pancreas delivers digestive juice to the small intestine through small tubes called ducts.

Liver. The liver produces a digestive juice called bile. The gallbladder stores bile between meals. When a person eats, the gallbladder squeezes bile through the bile ducts, which connect the gallbladder and liver to the small intestine. The bile mixes with the fat in food. The bile acids dissolve fat into the watery contents of the intestine, much like how detergents dissolve grease from a frying pan, so the intestinal and pancreatic enzymes can digest the fat molecules.

Small intestine. Digestive juice produced by the small intestine combines with pancreatic juice and bile to complete digestion. The body completes the breakdown of proteins, and the final breakdown of starches produces glucose molecules that absorb into the blood. Bacteria in the small intestine produce some of the enzymes needed to digest carbohydrates.

Read More

Fundamental & Derived Quantities

Science is concern with making sense out of the environment . The early stages of this “ search for sense” usually involve objects in the environment things that can be seen or touched. These could be objects you see every day, such as a glass of water, a moving automobile, or a running dog. One way is to assume that all events in nature have natural causes. We can then try to arrange a series of observation or tests to learn what those causes are. Science is the word that we apply to this process. The goal of science is to understand the world around us. There are, however, many important fields of human endeavor that study the world around us but are not considered sciences.

Scale  is anything that can be measured and expressed in value. If the terms of the direction and value, magnitude grouped into two, namely:

1.   Scalar or fundamental quantity, the quantity that only has value without having direction. Example: mass, length, time, energy, effort, temperature, pace and distance. 
2. Vector or derived quantity, the amount of which has a value and a direction. Example: style, weight, strong currents, velocity, acceleration and displacement.

Meanwhile, based on the type of unit, size grouped into two, namely:

a.    Scale Basic

Principal amount is the amount that the unit has been set in advance and are not composed of other quantities. Principal amount of seven scale. Seven units are based on the principal amount and the international system of units (SI) as indicated in the following table.

International system of units (SI) unit system means that the most widely used around the world, with international best practice.

b. Scale Derivatives 

 Scale derivative is a combination of units of the principal amount. Examples of broad scale derivative is a rectangular area. Area equal to the length multiplied by width, where length and width are both units of length. Note the magnitude derived tables, units and dimensions below.

 

Unit is a measure of a quantity used to measure. The types of units namely:

a. Raw Unit 

    Standard unit is the unit that has been recognized and its use internationally agreed    with the so-called tau international units (SI).

Example: meter, kilogram, and second.

International system of units is divided into two, namely:

1. MKS system (Meter Kilogram Sekon)

2. System CGS (Centimeter Gram Second)

b. Unit Not Raw 

    Non-standard unit is the unit that is not recognized internationally and is only used in a certain area. Example: fathoms, feet, legs, arms, tumbak, brick and steps 

Science works best when scientists every where read each other’s paper, check each other’s experiment and argue about what those experiments mean. Because most experiment involve measurement in which to present their findings. Scientists use the metric system of length, volume, mass, and temperature when describing experiments and data. The metric system is a decimal system based on the certain standards and scale on multiples of 10. The metric system is also known as the International system of Units or SI.

1. Length

    The basic unit of length in the metric system is a meter (m). One meter is roughly equivalent to 39,4 inchies, alittle longer than a yard. To measure objects and distance much larger or smaller than a meter by multiples of 10. A centimeter (cm) is 1/100 of a meter-about the width of the nail on your pinky. As you may have guessed, the prefix centi- means on hundredth. A milimeter (mm) is 1/1000 of a meter. The length-such as those used to describe living thing cells, pieces of cells, and molecules. To measure the distance much greater than a meter, scientists used a unit called the kilometer (km). One kilometer is contain 1000 meter and use prefix kilo-

 

2.    Volume

       Volume is the amount of space an object occupies. The basic metric unit of volume are the liter (L) for liquid and the cubic centimeter (cc or m³) for solids. A liter contain slighty more liquid than a quart. To measure small volume of liquids, scientists use fraction of a liter called milliliters (mL). There are 1000 milliliters in a single liter. A cubic centimeters is the volume of a solid that measures 1 cm by 1 cm by 1 cm. Keep in mind that 1 milliliter is equal in volume to 1 cubic centimeter or 1 mL=1 cc.

 

3.    Mass and Weight

        Mass is measure of the amount of matter in an object. Weight is a measure of the pull of gravity on that mass. In outer space, the weight of an object may vary with it’s position, but its mass always remain the same. On earth’s surface, however, an object’s mass and weight can usually be considered constant and are often used interchangeably. The basic metric unit scientists used to describe mass is the kilogram (kg). One kilogram is equal to approximately 2,2 pounds. The mass of small objects is measured in grams (g). One gram is 1/1000 of kilograms.

 

4.    Temperature 

        The metric system measures temperature using the Celcius scale (⁰C). On this scale water freezes at 0⁰C and boils at 100⁰C. Each celcius degree, therefore, represents exactly 1/100 of the temperature range between the freezing and boiling points of water. Normal human body temperature is about 37⁰C and comfortable room temperature is about 21⁰C. 

Measurement is something that is used to measure a quantity. A wide range of measuring instruments have a certain level of accuracy. It relies on the smallest scale measures. The smaller the scale indicated on the gauge, the higher precision instruments. Some examples of measuring instruments in accordance with the magnitude, namely:

a. Length Measurement

1. Ruler (ruler)

The bar is a long style with precision measuring up to 0.1 cm or 1 mm. On the reading scale, the position of the observer's eye should be perpendicular to the scale ruler in reading. 

2. Calipers

Calipers used to measure an object with a length of less than 1mm. Smallest scale or level of measurement accuracy up to 0.01 cm or 0.1 mm. Generally, calipers are used to measure the length of an object, the diameter of the ball, Ebal coins, and the inner diameter of the tube. Scale calipers have two readings, namely:

              a).   Main Scale / fixed, which is contained in the fixed jaw vernier caliper. 

 b). Vernier scale, the scale contained in the sliding jaw Dapa shifted / moved.

3. micrometer Screws

A micrometer screw gauge length with the smallest degree of accuracy. It is 0.01 mm or 0.001 cm. Smallest scale (scale Nonius) on micrometer screw located on the sliding jaw, while the major scale are the fixed jaw. Micrometer screw is used to measure the diameter of a round object and a very thin plate.

a.    Mass Measurement

Measuring instruments used to measure the mass of an object is the balance sheet. Based on how it works and the accuracy balance sheet is divided into three, namely:
1. Digital balance, the balance that works with electronic systems. Accurate and up to 0,001 g

2. O'Hauss balance, ie the balance sheet with a level of accuracy up to 0:01 g.

3. Equal arm balance, ie the balance sheet with a level of accuracy up to 1 mg or 0.001  

c.  Time Measurement 

     International unit for time is seconds or seconds. The second standard is the time needed by Cesium-133 atom to vibrate 9,192,631,770 times as much. The tools used to measure time, among other sundials, clocks, watches (with a precision of 1 second), and a stopwatch (nearest 0.1 second). 

 

Read More