# I have to make a file on sound,Work&energy

1
by Sapnapilania

2014-12-24T02:05:32+05:30

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Sound:
Sound is produced in a material medium when the source vibrates in time.  The vibrating source compresses the part of medium next to it when it moves forward and then increases pressure in that region (compression area).

When the vibrating source moves backwards, a low pressure region (rarefaction) is created. This pattern of pressure changes continues cyclically.  Sound is thus this disturbance (of compressions and rarefactions) travelling  at a fixed speed in the medium.  The sound waves are also called longitudinal waves.  Sound travels in terms of mechanical waves created by vibration of particles in the direction of propagation.  Sound cannot travel with out a medium or in vacuum.

velocity of sound =  √ ( Bulk modulus / density of medium)

Velocity of sound in air at normal pressure and temperature is about 340 m/sec.  Sound travels faster in a denser medium, due to high bulk modulus. Sound is produced due to conversion of energy from other forms.  Sound waves have a frequency f of vibration and a wavelength λ.  The wavelength is the distance between two successive rarefactions or two successive compressions.
velocity v = f * λ
When two sound waves meet each other, then there is an interference between them.  The waves may destruct each other or  add to each other , depending on their phase difference.  There are various characteristics of sound wave.

Pitch is the measure of shrillness in a voice.  Female voice has a higher pitch and a buffalo's voice has a low pitch.  Higher frequency gives a higher pitch.  Loudness of sound is related to the sound level, which is measured as logarithm of intensity of energy (or power) in the wave.  It is measured in decibels.  We can hear sound waves of frequency from 0 hertz to 20 kHz in general.

A combination of frequencies produced by a musical instrument is different from the combination of frequencies produced by another.  The quality of sound depends on the combination.  A musical instrument produces waves with a frequency (fundamental frequency) as well as its integral multiples (called harmonic notes).

When a moving car or train approaches a siren, then the (apparent) frequency heard by the person inside the train or car is different from the actual frequency of the siren source.  This is called Doppler's effect.   The Doppler effect is used by RADAR's to estimate the speed of approaching airplanes.

Intensity and Energy in a sound wave are proportional to square of frequency.   Interiors of various community halls or theaters are designed for proper acoustics, taking into account the reflections of sound waves from the ceiling and side walls.

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Work  Energy:

Energy is defined as capability to do work.  Work is useful way of consumption of energy.  When a force moves an object over a distance,  Work done =  Force * Displacement  * Cos θ,  where θ is the angle between force vector and displacement.

When an object falls through a height h, the work done by the gravitational field of Earth is equal to  force  * displacement = m g h. When work is done by (on) the system, its total energy reduces (increases) by the amount equal to the work done.

Work energy theorem says that the work done is equal to the change in kinetic energy of the system.Work done when a gas expands from volume V1 to V2 at a constant pressure P is equal to P (V2 - V1).  Work done when a mass m moves in a gravitational field due to a mass M at a distance d is  G M m / d.  Work done when an electric charge q moves across a voltage V is equal to qV.   Work done when a rope is twisted by an angle θ is equal to 1/2 K θ^2.
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Energy :

Energy is the ability to perform useful work.  Work is done when a change occurs in positions or speeds of objects or friction is overcome etc.Energy is inherently present in all matter as  E = m c^2, given by A. Einstein.  There are different forms of energy.

Energy is divided into two types.  Potential and kinetic.  Kinetic energy is associated with the movement of objects.  Potential energy is dependent on the position of the object in a field.Forms of energy are Mechanical, Sound energy (kinetic), Gravitational potential energy, Electrical potential energy, Magnetic potential energy, chemical energy (in terms of attractions of atoms, molecules), nuclear energy (due to sub atomic particles), heat energy, electromagnetic radiation energy.

Heat energy is the form of energy that flows from one system to another depending on gradient in temperature.  Chemical energy is the energy released (absorbed) when bonds between atoms and molecules are broken and formed in chemical compounds.Kinetic energy of a body of mass m with a velocity v is equal to 1/2 m v^2.  Energy stored in a spring (of spring constant k) when it is compressed by an amount x is equal to 1/2 k x^2.

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