Viscous Damping

It is encountered by bodies moving at moderate speed through liquid. This type of damping leads to a resisting force proportional to the velocity. The damping force

Fd ∞ dx/dt


Fd =cx


‘c’ is the constant of proportionality and is called viscous damping Co-eff. With the dimension of N-S/m

Types of Damping

1. Viscous Damping
2. Colomb Damping
3. Solid or structural Damping
4. Slip or Intrefacial damping

Vibrations

The study of vibration is concerned with the oscillatory motion of bodies and the forces associated with them. All bodies possesing mass and elasticity are capable of vibrating. Thus most enginerring machines and structure experience vibration to some degree and their design generally requires consideration of their oscillatory behaviour.

MEASUREMENT OF INTENSITY OF SOUND

The intensity of sound is defined as the quantity of energy propagating through a unit area per unit time, the direction of propagation being perpendicular to the area. The amount of power transmitted is measured in Watt/m². A convenient unit is microwatts/m².

According to Weber Fechner law in psychology, the loudness of a sound as judged by the ear is proportional to the logarithm of the intensity. If I1 and I0 represent the intensities ot two sounds of a particular frequency and L1 and L0 the corresponding measure of loudness then L1 = KlogI1 and L0=KlogI0. The difference in loudness technically known as intensity Level, L between them is given by

L = L1 – L2 =K[logI1 – logI0]

L = K log( I1 / I0 )

Where K is a constant that depends on the units and I0 is some standard reference intensity arbitrarily takes as 10

PROPAGATION OF SOUND

Sound is produced by a vibrating body.A material medium is necessary for the propagation of sound waves .In wave motion momentum and energy are transferred.Charactrestics of wave motion

1. Wave motion is a disturbance produced in the medium by the repeated periodic motion of the particles of the medium.

2. Only the wave travels forward whereas the particles of the medium vibrate about their mean position.

3. there is regular phase change between various particles of the medium. The particle ahead starts a vibrating a little later than the particles preceding it.

4. the velocity of the wave is different from the velocity with which the particles of the medium are vibrating about their mean position. The wave travels with a uniform velocity whereas the velocity of the particle is different at different positions. It is maximum at the mean position and zero at the extreme positions of the particles. There are two types of wave motions

a. Transverse wave

b. Longitudinal Wave

Sound waves are longitudinal waves and light waves are transverse waves. Figure 1 shows the formation and propagation of transverse and longitudinal wave.

A sound wave is propagated and conveyed to the ear by means of the intervening layers of air. Consider a vibrating tuning fork as shown in figure 2. Let us confine our attention to the right hand prong only. When it moves towards the right, it compresses the layer of air in front of it and as a consequence the pressure of this layer will be greater than the adjacent layers. It tends to relieve the strain thus created , by compressing them. These in turn hand on the compression. Thus a pluse of compression will travel onwards to the right. Again when the prong moves towards the left rarefraction are sent out in regular succession. These waves at last reach the ear and set the tympanic membrane, which is ultimately transmitted via a system of bones and cords to the brain and causes the mental sensation called sound

---

Polymerisation

Polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymers chains. There are many forms of polymerization and different systems exist to categorize them.

Polymers such as PVC are generally referred to as "homopolymers" as they consist of repeated long chains or structures of the same monomer unit, whereas polymers that consist of more than one molecule are referred to as "co-polymers".

Homosexuality

Homosexuality refers to romantic or sexual attraction or behaviour among members of the same sex, situationally or in an enduring disposition. As a sexual orientation, homosexuality is considered to lie within the hetrosexual-homosexual continuum of human sexuality, and refers to an individual’s identity based on those attractions and membership in a community of others who share them.

Homosexuality is found in many animal species. The prevalence of homosexuality among humans is difficult to determine accurately; studies suggest between two and twenty percent of the population exhibit some degree of homosexual tendency, though in many earlier cultures homosexual relations were highly prevalent. Throughout history, individual aspects of homosexuality have been admired according to various societies' sexual norms. When praised, those aspects were seen as a way to improve society; when condemned, particular activities were seen as a sin or a disease, and some homosexual behavior was prohibited by law. Since the middle of the 20th century homosexuality has been gradually delisted as a disease and decriminalized in nearly all developed countries. However, the legal status of homosexual relations varies widely by countries and there remain jurisdictions in which certain homosexual behaviors are crimes with severe penalties including death.

Many homosexual people hide their feelings and activities out of fear of disapproval or violence; they are commonly said to be closeted. Openly declaring one's orientation is known as coming out of the closet. Efforts toward emancipation of homosexuality as it is currently understood began in the 1860s; since the mid-1950s there has been an accelerating trend towards increased visibility, acceptance, and civil rights for lesbian, gay and bisexual people. Nevertheless, homophobia persists, and in particular young people subjected to it are at greater risk of socialization difficulties including suicide. Currently the most common adjectives in use are lesbian for women and gay for men, though some prefer other terms or none at all.

Prostitution

Prostitution is defined as the act or practice of engaging in sex acts for hire. In most cultures, prostitution is viewed as a deviant profession, either discouraged or illegal, however motivations vary from the implications of those potentially exposed to that activity to whether it constitutes or not an explotitative practice.

In colloquial usage, the word "prostitute" is sometimes generalized to mean the act or an instance of offering or devoting one's talent to an unworthy use or cause.