Applied Science


Chemistry is the science that deals with the properties, composition, and structure of substances (defined as elements and compounds), the transformations that they undergo, and the energy that is released or absorbed during these processes. Every substance, whether naturally occurring or artificially produced, consists of one or more of the hundred-odd species of atoms that have been identified as elements. Although these atoms, in turn, are composed of more elementary particles, they are the basic building blocks of chemical substances; there is no quantity of oxygen, mercury, or gold, for example, smaller than an atom of that substance. Chemistry, therefore, is concerned not with the subatomic domain but with the properties of atoms and the laws governing their combinations and with how the knowledge of these properties can be used to achieve specific purposes.

Common Alloys




55% copper, 45% zinc


copper, tin

cast iron

iron, carbon, silicon, manganese,


trace impurities


copper, nickel




tin, antimony, copper


tin, lead

stainless steel

iron, carbon, chromium, nickel


iron, carbon

sterling silver

silver, copper


Physics is the science that deals with the structure of matter and the interactions between the fundamental constituents of the observable universe. The basic physical science, its aim is the discovery and formulation of the fundamental laws of nature. In the broadest sense, physics (from the Greek physikos) is concerned with all aspects of nature on both the macroscopic and submicroscopic levels. Its scope of study encompasses not only the behavior of objects under the action of given forces but also the nature and origin of gravitational, electromagnetic, and nuclear force fields. Its ultimate objective is the formulation of a few comprehensive principles that bring together and explain all such disparate phenomena. Physics can, at base, be defined as the science of matter, motion, and energy. Its laws are typically expressed with economy and precision in the language of mathematics.

Weight, Mass, and Density

Mass, strictly defined, is the quantitative measure of inertia, the resistance a body offers to a change in its speed or position when force is applied to it. The greater the mass of a body, the smaller the change produced by an applied force. In more practical terms, it is the measure of the amount of material in an object, and in common usage is often expressed as weight. However, the mass of an object is constant regardless of its position, while weight varies according to gravitational pull.

In the International System of Units (SI; the metric system), the kilogram is the standard unit of mass, defined as equaling the mass of the international prototype of the kilogram, currently a platinum-iridium cylinder kept at Sevres, near Paris, France; it is roughly equal to the mass of 1,000 cubic centimeters of pure water at the temperature of its maximum density. In the US customary system, the unit is the slug, defined as the mass which a one pound force can accelerate at a rate of one foot per second per second, which is the same as the mass of an object weighing 32.17 pounds on the earth’s surface.

Weight is the gravitational force of attraction on an object, caused by the presence of a massive second object, such as the Earth or Moon. Weight is the product of an object’s mass and the acceleration of gravity at the point where the object is located. A given object will have the same mass on the Earth’s surface, on the Moon, or in the absence of gravity, while its weight on the Moon would be about one sixth of its weight on the Earth’s surface, because of the Moon’s smaller gravitational pull (due in turn to the Moon’s smaller mass and radius), and in the absence of gravity the object would have no weight at all.

Weight is measured in units of force, not mass, though in practice units of mass (such as the kilogram) are often substituted because of mass’s relatively constant relation to weight on the Earth’s surface. The weight of a body can be obtained by multiplying the mass by the acceleration of gravity. In SI, weight is expressed in newtons, or the force required to impart an acceleration of one meter per second per second to a mass of one kilogram. In the US customary system, it is expressed in pounds.

Density is the mass per unit volume of a material substance. It offers a convenient means of obtaining the mass of a body from its volume, or vice versa; the mass is equal to the volume multiplied by the density, while the volume is equal to the mass divided by the density. In SI, density is expressed in kilograms per cubic meter.

The Internet is a dynamic collection of computer networks that has revolutionized communications and methods of commerce by enabling those networks around the world to interact with each other. Sometimes referred to as a “network of networks,” the Internet was developed in the United States in the 1970s but was not widely used by the general public until the early 1990s. By early 2008 nearly 1.5 billion people, or roughly 22% of the world’s population, were estimated to have access to the Internet. It is widely assumed that at least half of the world’s population will have some form of Internet access by 2010 and that wireless access will play a growing role.

The Internet is so powerful and general that it can be used for almost any purpose that depends on the processing of information, and it is accessible by every individual who connects to one of its constituent networks. It supports human communication via electronic mail (e-mail), real-time “chat rooms,” instant messaging (IM), newsgroups, and audio and video transmission and allows people to work collaboratively at many different locations. It supports access to information by many applications, including the World Wide Web, which uses text and graphical presentations. Publishing has been revolutionized, as whole novels and reference works are available on the Web, and periodicals, including data prepared daily for an individual subscriber (such as stock market reports or news summaries), are also common. The Internet has attracted a large and growing number of “e-businesses” (including subsidiaries of traditional “brick-and-mortar” companies) that carry out most of their sales and services over the Internet.

While the precise structure of the future Internet is not yet clear, many directions of growth seem apparent. One is the increased availability of wireless access, enabling better real-time use of Web-managed information. Another future development is toward higher backbone and network access speeds. Backbone data rates of10 billion bits (10 gigabits) per second are readily available today, but data rates of 1 trillion bits (1 terabit) per second or higher will eventually become commercially feasible. At very high data rates, high-resolution video, for example, would occupy only a small fraction of available bandwidth, and remaining bandwidth could be used to transmit auxiliary information about the data being sent, which in turn would enable rapid customization of displays and prompt resolution of certain local queries.

Communications connectivity will be a key function of a future Internet as more machines and devices are interconnected. Since the Internet Engineering Task Force published its 128-bit IP address standard in 1998, the increased number of available addresses (2128, as opposed to 232 under the previous standard) allowed almost every electronic device imaginable to be assigned a unique address. Thus the expressions “wired” office, home, and car may all take on new meanings, even if the access is really wireless.

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