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Metre Per Second

Metre per second

Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector), defined by distance in metres divided by time in seconds. The symbol is m/s, or equivalently, m s^-1.

Conversions

1 metre per second is equivalent to:
- 3.2808 feet per second
- 2.2369 miles per hour
- 3.6 km/h

United States

:For alternative meanings, see the disambiguation page for US, USA, United States, or American. The United States of America is a federal democratic republic situated primarily in central North America. It comprises 50 states and one federal district, and has several territories. It is also referred to, with varying formality, as the United States, the U.S., the U.S.A., the States, or simply and most commonly, America. The official founding date of the United States is July 4, 1776, when the Second Continental Congress—representing thirteen British colonies—adopted the Declaration of Independence. However, the structure of the government was profoundly changed in 1788, when the states replaced the Articles of Confederation with the United States Constitution. The date on which each of the fifty states adopted the Constitution is typically regarded as the date that state "entered the Union" (became part of the United States). Since the mid-20th century, following World War II, the United States has emerged as a dominant global influence in economic, political, military, scientific, technological, and cultural affairs.

Geography and climate

The United States shares land borders with Canada (to the north) and Mexico (to the south), and territorial water boundaries with Canada, Russia, the Bahamas, and numerous smaller nations. It is otherwise bounded by the Pacific Ocean and the Bering Sea, in the west; the Arctic Ocean, in the northernmost areas; and the Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea, in the eastern and southeastern areas. Forty-eight of the states are in the single region between Canada and Mexico; this group is referred to, with varying precision and formality, as the continental or contiguous United States, sometimes abbreviated CONUS, and as the Lower 48. Alaska, which is not included in the term contiguous United States, is at the northwestern end of North America, separated from the Lower 48 by Canada. The archipelago of Hawaii is in the Pacific Ocean. The capital city, Washington, District of Columbia is a federal district located on land donated by the state of Maryland. (Virginia also donated land, but it was returned in 1847.) The United States also has overseas territories with varying levels of independence and organization. When inland water is included in the total area, only Russia and Canada are larger than the United States; if inland water is excluded, China ranks third and the U.S. ranks fourth. The United States' total area is 3,718,711 square miles (9,631,418 km²), of which land makes up 3,537,438 square miles (9,161,923 km²) and water makes up 181,273 square miles (469,495 km²). The United States' landscape is one of the most varied among those of the world's nations: among its many features are temperate forestland and rolling hills, on the east coast; mangrove, in Florida; the Great Plains, in the center of the country; the Mississippi–Missouri river system; the Great Lakes, four of the five of which are shared with Canada; the Rocky Mountains, west of the Great Plains; deserts and temperate coastal zones, west of the Rocky Mountains; and temperate rain forests, in the Pacific northwest. Alaska's tundra, and the volcanic, tropical islands of Hawaii add to the geographic diversity. Hawaii The climate varies along with the landscape, from tropical in Hawaii and southern Florida to tundra in Alaska and atop some of the highest mountains. Most of the North and East experience a temperate continental climate, with warm summers and cold winters. Most of the South experiences a subtropical humid climate with mild winters and long, hot, humid summers. Rainfall decreases markedly from the humid forests of the Eastern Great Plains to the semi-arid shortgrass prairies on the high plains abutting the Rocky Mountains. Arid deserts, including the Mojave, extend through the lowlands and valleys of the southwest, from westernmost Texas to California and northward throughout much of Nevada. Some parts of California have a Mediterranean climate. Rainforests line the windward mountains of the Pacific Northwest from Oregon to Alaska.

History

American history started with the migration of people from Asia across the Bering land bridge approximately 12,000 years ago following large animals that they hunted into the Americas. These Native Americans left evidence of their presence in petroglyphs, burial mounds, and other artifacts. It is estimated that 2-9 million people lived in the territory now occupied by the U.S. before European contact, and the subsequent introduction of foreign diseases such as small pox that greatly diminished the native populations. Some advanced societies were the Anasazi of the southwest, who inhabited Chaco Canyon, and the Woodland Indians, who built Cahokia, located near present-day St Louis, a city with a population of 40,000 at its peak in AD 1200. Vikings first visited North America around 1000, but did not settle permanently. Following the discovery voyages of Christopher Columbus around 1492, other Europeans began to explore and settle there. During the 1500s and 1600s, the Spanish settled parts of the present-day Southwest and Florida, founding St. Augustine, Florida in 1565 and Santa Fe (in what is now New Mexico) in 1607. The first successful English settlement was at Jamestown, Virginia, also in 1607. Within the next two decades, several Dutch settlements, including New Amsterdam (the predecessor to New York City), were established in what are now the states of New York and New Jersey. In 1637, Sweden established a colony at Fort Christina (in what is now Delaware), but lost the settlement to the Dutch in 1655. This was followed by extensive British settlement of the east coast. The British colonists remained relatively undisturbed by their home country until after the French and Indian War, when France ceded Canada and the Great Lakes region to Britain. Britain then imposed taxes on the 13 colonies, widely regarded by the colonists as unfair because they were denied representation in the British Parliament. Tensions between Britain and the colonists increased, and the thirteen colonies eventually rebelled against British rule. British Parliament, George Washington (1789-1797).]] In 1776, the 13 colonies split from Great Britain and formed the United States, the world's first constitutional and democratic federal republic, after their Declaration of Independence of that year, and the Revolutionary War (1775 to 1783). The original political structure was a confederation in 1777, ratified in 1781 as the Articles of Confederation. After long debate, this was supplanted by the Constitution in 1789, forming a more centralized federal government. Prior to all these was the Albany Congress in 1754, in which a union was first seriously proposed. From early colonial times, there was a shortage of labor, which encouraged unfree labor, particularly indentured servitude and slavery. In the mid-19th century, a major division occurred in the United States over the issue of states' rights and the expansion of slavery. The northern states had become opposed to slavery, while the southern states saw it as necessary for the continued success of southern agriculture and wanted it expanded to the territories. Several federal laws were passed in an attempt to settle the dispute, including the Missouri Compromise and the Compromise of 1850. The dispute reached a crisis in 1861, when seven southern states seceded¹ from the Union and formed the Confederate States of America, leading to the Civil War. Soon after the war began, four more southern states seceded. During the war, Abraham Lincoln issued the Emancipation Proclamation, mandating the freedom of all slaves in states in rebellion, though full emancipation did not take place until after the end of the war in 1865, the dissolution of the Confederacy, and the Thirteenth Amendment took effect. The Civil War effectively ended the question of a state's right to secede, and is widely accepted as a major turning point after which the federal government became more powerful than state governments. Thirteenth Amendment). The title of the painting, from a 1726 poem by Bishop Berkeley, was a phrase often quoted in the era of Manifest Destiny, expressing a widely held belief that civilization had steadily moved westward throughout history. [http://americanart.si.edu/t2go/1lw/1931.6.1.html (more)] ]] During the 19th century, many new states were added to the original 13 as the nation expanded across the continent. Manifest Destiny was a philosophy that encouraged westward expansion in the United States. As the population of the Eastern states grew and as a steady increase of immigrants entered the country, settlers moved steadily westward across North America. In the process, the U.S. displaced most American Indian nations. This displacement of American Indians continues to be a matter of contention in the U.S. with many tribes attempting to assert their original claims to various lands. In some areas American Indian populations were reduced by foreign diseases contracted through contact with European settlers, and US settlers acquired those emptied lands. In other instances American Indians were removed from their traditional lands by force. Though some would say the U.S. was not a colonial power until the Spanish-American War when it acquired Puerto Rico, Guam and the Philippines, the dominion exercised over land in North America the United States claimed is essentially colonial. The Philippines became independent in 1946. During this period, the nation also became an industrial power. This continued into the 20th century, which has been termed "the American Century" because of the nation's overriding influence on the world. The US became a center for innovation and technological development; major technologies that America either developed or was greatly involved in improving include the telephone, television, computer, the Internet, nuclear weapons, nuclear power, aviation, and aeronautics. In addition to the Civil War, another major traumatic experience for the nation was the Great Depression (1929 to 1939). The nation has also taken part in several major foreign wars, including World War I and World War II (in both of which the US later joined the Allies). During the Cold War, the US was a major player in the Korean War and Vietnam War, and, along with the Soviet Union, was considered one of the world's two "superpowers". With the collapse of the Soviet Union, the US emerged as the world's leading economic and military power. Beginning in the 1990s, the United States became very involved in police actions and peacekeeping, including actions in Kosovo, Haiti, Somalia and Liberia, and the first Persian Gulf War driving Iraq out of Kuwait. After attacks on the World Trade Center and the Pentagon on September 11, 2001, the United States and other allied nations found themselves involved in what has come to be called the "War on Terrorism," which has primarily encompassed military actions in both Afghanistan and Iraq.

Government

Iraq of the United States.]]

Republic and suffrage

The United States is an example of a constitutional republic, with a government composed of and operating through a set of limited powers imposed by its design and enumerated in the United States Constitution. Specifically, the nation operates as a presidential democracy. There are three levels of government: federal, state, and local. Officials of each of these levels are either elected by eligible voters via secret ballot or appointed by other elected officials. Americans enjoy almost universal suffrage from the age of 18 regardless of race, sex, or wealth. There are some limits, however: felons are disenfranchised and in some states former felons are likewise. Furthermore, the national representation of territories and the federal district of Washington, DC in Congress is limited: residents of the District of Columbia are subject to federal laws and federal taxes but their only Congressional representative is a non-voting delegate.

Federal government

The federal government is the national government, comprising the Legislative Branch (led by Congress), the Executive Branch (led by the President), and the Judicial Branch (led by the Supreme Court). These three branches were designed to apply checks and balances on each other. The Constitution limits the powers of the federal government to defense, foreign affairs, the issuing and management of currency, the management of trade and relations between the states, and the protection of human rights. In addition to these explicitly stated powers, the federal government—with the assistance of the Supreme Court—has gradually extended these powers into such areas as welfare and education, on the basis of the "necessary and proper" clause of the Constitution.

The Congress

necessary and proper The Congress of the United States is the legislative branch of the federal government of the United States. It is bicameral, comprising the House of Representatives and the Senate. The House of Representatives consists of 435 members, each of whom represents a congressional district and serves for a two-year term. House seats are apportioned among the states by population; in contrast, each state has two Senators, regardless of population. There are a total of 100 senators, who serve six-year terms. The powers of Congress are limited to those enumerated in the Constitution; all other powers are reserved to the states and the people. The Constitution also includes the necessary-and-proper clause, which grants Congress the power to "make all laws which shall be necessary and proper for carrying into execution the foregoing powers."

The President

necessary-and-proper clause At the top level of the executive branch is the President of the United States. The President and Vice-President are elected as 'running mates' for four-year terms by the Electoral College, for which each state, as well as the District of Columbia, is allocated a number of seats based on its representation (or ostensible representation, in the case of D. C.) in both houses of Congress (see U.S. Electoral College). The relationship between the President and the Congress reflects that between the English monarchy and parliament at the time of the framing of the United States Constitution. Congress can legislate to constrain the President's executive power, even with respect to his or her command of the armed forces; however, this power is used only very rarely—a notable example was the constraint placed on President Richard Nixon's strategy of bombing Cambodia during the Vietnam War. The President cannot directly propose legislation, and must rely on supporters in Congress to promote his or her legislative agenda. The President's signature is required to turn congressional bills into law; in this respect, the President has the power—only occasionally used—to veto congressional legislation. Congress can override a presidential veto with a two-thirds majority vote in both houses. The ultimate power of Congress over the President is that of impeachment or removal of the elected President through a House vote, a Senate trial, and a Senate vote. The threat of using this power has had major political ramifications in the cases of Presidents Andrew Johnson, Richard Nixon, and Bill Clinton. The President makes around 2,000 executive appointments, including members of the Cabinet and ambassadors, which must be approved by the Senate; the President can also issue executive orders and pardons, and has other Constitutional duties, among them the requirement to give a State of the Union address to Congress once a year. Although the President's constitutional role may appear to be constrained, in practice, the office carries enormous prestige that typically eclipses the power of Congress: the Presidency has justifiably been referred to as 'the most powerful office in the world'. The Vice President is first in the line of succession, and is the President of the Senate ex officio, with the ability to cast a tie-breaking vote. The members of the President's Cabinet are responsible for administering the various departments of state, including the Department of Defense, the Justice Department, and the State Department. These departments and department heads have considerable regulatory and political power, and it is they who are responsible for executing federal laws and regulations. George W. Bush is the 43rd President, currently serving his second term.

The Courts

George W. Bush The highest court is the Supreme Court, which consists of nine justices. The court deals with federal and constitutional matters, and can declare legislation made at any level of the government as unconstitutional, nullifying the law and creating precedent for future law and decisions. Below the Supreme Court are the courts of appeals, and below them in turn are the district courts, which are the general trial courts for federal law. Separate from, but not entirely independent of, this federal court system are the individual court systems of each state, each dealing with its own laws and having its own judicial rules and procedures. A case may be appealed from a state court to a federal court only if there is a federal question; the supreme court of each state is the final authority on the interpretation of that state's laws and constitution.

State and local governments

supreme court of each state. Note that Alaska and Hawaii are shown at different scales, and that the Aleutian Islands and the uninhabited Northwestern Hawaiian Islands are omitted from this map.]] The state governments have the greatest influence over people's daily lives. Each state has its own written constitution and has different laws. There are sometimes great differences in law and procedure between the different states, concerning issues such as property, crime, health, and education. The highest elected official of each state is the Governor. Each state also has an elected legislature (bicameral in every state except Nebraska), whose members represent the different parts of the state. Of note is the New Hampshire legislature, which is the third-largest legislative body in the English-speaking world, and has one representative for every 3,000 people. Each state maintains its own judiciary, with the lowest level typically being county courts, and culminating in each state supreme court, though sometimes named differently. In some states, supreme and lower court justices are elected by the people; in others, they are appointed, as they are in the federal system. The institutions that are responsible for local government are typically town, city, or county boards, making laws that affect their particular area. These laws concern issues such as traffic, the sale of alcohol, and keeping animals. The highest elected official of a town or city is usually the mayor. In New England, towns operate directly democratically, and in some states, such as Rhode Island and Connecticut, counties have little or no power, existing only as geographic distinctions. In other areas, county governments have more power, such as to collect taxes and maintain law enforcement agencies.

Political divisions

With the Declaration of Independence, the thirteen colonies proclaimed themselves to be nation states modeled after the European states of the time. Although considered as sovereigns initially, under the Articles of Confederation of 1781 they entered into a "Perpetual Union" and created a fully sovereign federal state, delegating certain powers to the national Congress, including the right to engage in diplomatic relations and to levy war, while each retaining their individual sovereignty, freedom and independence. But the national government proved too ineffective, so the administrative structure of the government was vastly reorganized with the United States Constitution of 1789. Under this new union, the continued status of the individual states as sovereign nation states fell into dispute in 1861, as several states attempted to secede from the union; in response, then-President Abraham Lincoln claimed that such secession was illegal, and the result was the American Civil War. Since the Union victory in 1865, the independent status of the individual states has not been broached again by any state, and the status of each state within the union has been deemed by mainstream officials and academics to be settled as being subordinate to the union as a whole. In subsequent years, the number of states grew steadily due to western expansion, the purchase of lands by the national government from other nation states, and the subdivision of existing states, resulting in the current total of 50. The states are generally divided into smaller administrative regions, including counties, cities and townships. The United States–Canadian border is the longest undefended political boundary in the world. The U.S. is divided into three distinct sections:
- the "continental United States," also known as "the Lower 48" and more accurately termed the conterminous, coterminous or contiguous United States
- Alaska, which is physically connected only to Canada
- the archipelago of Hawaii, in the central Pacific Ocean. The United States also holds several other territories, districts, and possessions, notably the federal district of the District of Columbia, which is the nation's capital, and several overseas insular areas, the most significant of which are American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the United States Virgin Islands. The Palmyra Atoll is the United States' only incorporated territory; it is unorganized and uninhabited. The United States Navy has held a base at a portion of Guantanamo Bay, Cuba, since 1898. The United States government possesses a lease to this land, which only mutual agreement or United States abandonment of the area can terminate. The present Cuban government of Fidel Castro disputes this arrangement, claiming Cuba was not truly sovereign at the time of the signing. The United States argues this point moot because Cuba apparently ratified the lease post-revolution, and with full sovereignty, when it cashed one rent check in accordance with the disputed treaty.

Foreign relations and military

sovereign] The immense military and economic dominance of the United States has made foreign relations an especially important topic in its politics, with considerable concern about the image of the United States throughout the world. Reactions towards the United States by other nationalities are often strong, ranging from uninhibited admiration and mimicking of all things American to anti-Americanism. US foreign policy has swung about several times over the course of its history between the poles of strict isolationism and imperialism and everywhere in between. Three of the nation's four military branches are administered by the Department of Defense: the Army, the Navy (including the Marine Corps), and the Air Force. The Coast Guard falls under the jurisdiction of the Department of Homeland Security in peacetime, but is placed under the Department of the Navy in time of war. The combined United States armed forces consist of 1.4 million active duty personnel, along with several hundred thousand each in the Reserves and the National Guard. Military conscription ended in 1973. The United States Armed forces are considered to be the most powerful military (of any sort) on Earth and their force projection capabilities are unrivaled by any other nation. The 2005 defense budget amounted to $401.7 billion, which is an increase of 4% over 2004 and of 35% since 2001. Over 50% of that number is spent in research & development. (For comparison, in 2004 the European Union (considered as the second-largest military force) had a combined total of 1.6 million troops, and a defense budget of €160 billion, with less than 10% of that being spent on R&D.)

Largest cities

The United States has dozens of major cities, including 11 of the 55 global cities of all types — with three "alpha" global cities: New York City, Los Angeles, and Chicago. The figures expressed below are for populations within city limits. A different ranking is evident when considering U.S. metro area populations, although the top three would be unchanged. Note that some cities not listed (such as Atlanta, Boston, Las Vegas, Miami, Nashville, New Orleans, Seattle, and Washington, D.C.) are still considered important on the basis of other factors and issues, including culture, economics, heritage, and politics. The twenty largest cities, based on the United States Census Bureau's 2004 estimates, are as follows:

Economy

The United States has the largest single-country economy in the world, with a per-capita gross domestic product of $40,100. In this market-oriented economy, private individuals and business firms make most of the decisions, and the federal and state governments buy needed goods and services predominantly in the private marketplace. gross domestic product The largest industry of the U.S. is now service, which employs roughly three quarters of the U.S. work force. The United States has many natural resources, including oil and gas, metals, and such minerals as gold, soda ash, and zinc. In agriculture, the U.S. is a top producer of, among other crops, corn, soy beans, and wheat; the United States is a net exporter of food. The U.S. manufacturing sector produces goods such as, cars, airplanes, steel, and electronics, among many others. Economic activity varies greatly from one part of the country to another, with many industries being largely dependent on a certain city or region; New York City is the center of the American financial, publishing, broadcasting, and advertising industries; Silicon Valley is the country’s primary location for high-technology companies, while Los Angeles is the most important center for film production. The Midwest is known for its reliance on manufacturing and heavy industry, with Detroit, Michigan, serving as the center of the American automotive industry; the Great Plains are known as the "breadbasket" of America for their tremendous agricultural output; the intermountain region serves as a mining hub and natural gas resource; the Pacific Northwest for fish and timber, while Texas is largely associated with the oil industry; the Southeast is a major hub for both medical research and the textiles industry. Several countries continue to link their currency to the dollar or even use it as a currency (such as Ecuador), although this practice has subsided since the collapse of the Bretton Woods system. Many markets are also quoted in dollars, such as those of oil and gold. The dollar is also the predominant reserve currency in the world, and more than half of global reserves are in dollars. The largest trading partner of the United States is Canada (19%), followed by China (12%), Mexico (11%), and Japan (8%). More than 50% of total trade is with these four countries. In 2003, the United States was ranked as the third most visited tourist destination in the world; its 40,400,000 visitors ranked behind France's 75,000,000 and Spain's 52,500,000. Labor unions have existed since the 19th century, and grew large and powerful from the 1930s to the 1950s. See Labor history of the United States. Since 1970 they have shrunk in the private sector and now cover fewer than 8% of the workers. However union membership has grown rapidly in the public sector, especially among teachers, nurses, police, postal workers, and municipal clerks. There have been few strikes in recent years. The United States' imports exceed exports by 80%, leading to an annual trade deficit of $700,000,000,000, or 6% of gross domestic product. It is the largest debtor nation in the world, with total gross foreign debt of over $13,000,000,000,000 (2005 estimate); and it absorbs more than 50% of global savings annually. Since the 1980s, the U.S. has increased the use of neoliberal economic policies that reduce government intervention and reduce the size of the welfare state, backing away from the more interventionist Keynsian economic policies that had been in favor since the Great Depression. As a result, the United States provides fewer government-delivered social welfare services than most industrialized nations, choosing instead to keep its tax burden lower and relying more heavily on the free market and private charities. Sixteen states and the District of Columbia have minimum wages higher than the national level ($5.15 per-hour), including the highest, Washington State at $7.35. Twenty-six states are the same as the federal level; two--Ohio and Kansas--are below; and six do not have state laws. America's wealth is relatively highly concentrated. The average C.E.O. earns 500 times the typical amount a worker grosses, this is up from 25 times in the late 1970s. In terms of wealth the top 1% of Americans own 40% of all assets and 50.1% of the country's income goes to the top twenty percent of households. Average wages for the majority of employees have been largely stagnating since the 1970s. America's poverty line defined as a family of four earning less than $19,157 is at 12.7% of the general population. Approximately one out of every five children in the United States grows up below the official poverty line. Among racial groups; African Americans have the lowest median income while Asians had the highest. Regionally, the southern states had the lowest median incomes while the West Coast and New England had the highest. The current Federal Reserve Chairman Alan Greenspan remarked that the U.S.’s growing income inequality since the 1970s is, "not the type of thing which a democratic society - a capitalist democratic society - can really accept without addressing."[http://www.csmonitor.com/2005/0614/p01s03-usec.html?s=itm] However, Greenspan also noted, "...you can look at the system and say it's got a lot of problems to it, and sure it does. It always has. But you can't get around the fact that this is the most extraordinarily successful economy in history."

Transportation

Alan Greenspan ]] Because the United States is a relatively young nation, most of the development of U.S. cities has taken place since the invention of the automobile. To link its vast territory, the United States built a network of high-capacity, high-speed highways, of which the most important element is the Interstate Highway system, commissioned in the 1950s by President Dwight D. Eisenhower and modeled after the German Autobahn. The United States also has a transcontinental rail system, which is used for moving freight across the lower forty-eight states. Passenger rail service is provided by Amtrak, which serves forty-six of the lower forty-eight states. Many cities in the United States have extensive mass-transit systems. New York City operates one of the world's largest and most heavily used subway systems. The regional rail and bus networks that extend into Long Island, New Jersey, Upstate New York, and Connecticut are among the most heavily used in the world. Air travel is often preferred for destinations over 300 miles (500 kilometers) away. In terms of passengers, seventeen of the world's thirty busiest airports in 2004 were in the U.S., including the world's busiest, Hartsfield-Jackson Atlanta International Airport; in terms of cargo, in the same year, twelve of the world's thirty busiest airports were in the U.S., including the world's busiest, Memphis International Airport. There are several major seaports in the United States; the three busiest are the Port of Los Angeles, California; the Port of Long Beach, California; and the Port of New York and New Jersey. Others include Houston, Texas; Charleston, South Carolina; Savannah, Georgia; Miami, Florida; Portland, Oregon; San Francisco, California; Boston, Massachusetts; Philadelphia, Pennsylvania; and Seattle, Washington; plus, outside the contiguous forty-eight states, Anchorage, Alaska, and Honolulu, Hawaii.

Society

Demographics

Hawaii The mean center of the U.S. population continues to drift farther west and south. The fastest growing region is the western United States followed by the southern portion. According to Census 2000, the states that saw the greatest increases from 1990 were: Nevada (66.3%), Arizona (40%), Colorado (30.6%), Utah (29.6%), Idaho (28.5%), Georgia (26.4%), Florida (23.5%), Texas (22.8%), North Carolina (21.4%), and Washington (21.1%). [http://www.census.gov/population/cen2000/phc-t2/tab03.pdf]

Ethnicity and race

:Main article: Racial demographics of the United States The United States is a very racially diverse country. According to the 2000 census, it has 31 ethnic groups with at least one million members each, and numerous others represented in smaller amounts. The majority of Americans descend from white European immigrants who arrived at the establishment of the first colonies (most after Reconstruction). This majority--69.1% in 2000--decreases each year, and is expected to become a plurality within a few decades. The most frequently stated European ancestries are German (15.2%), Irish (10.8%), English (8.7%), Italian (5.6%) and Scandinavian (3.7%). Many immigrants also hail from Slavic countries such as Poland and Russia. Other significant immigrant populations came from eastern and southern Europe and French Canada. Russia Hispanics from Mexico and South and Central America are the largest minority group in the country, comprising 12.5% of the population (2000 census). People of Mexican descent made up 7.3% of the population in the 2000 census, and this proportion is expected to increase significantly in the coming decades. About 12.3% (2000 census) of the American people are African Americans (Blacks). African Americans are spread throughout the country, but their presence is largest in the South. Asian Americans--including Native Hawaiians and Pacific Islanders--are a third significant minority (3.7% of the population in 2000). Most Asian Americans are concentrated on the West Coast and Hawaii. The largest groups are immigrants or descendants of emigrants from the Philippines, China, India, Vietnam, South Korea, and Japan. Indigenous peoples in the United States, such as American Indians and Inuit, make up 0.9% of the population (2000 census). About 35% live on Indian reservations.

Religion

Polls estimate that just under 80 percent of Americans are Christians of various denominations. The other 20 percent comprises other religions such as Hinduism, Judaism, Islam, and Buddhism, other various faiths, and those without a specific religion. The United States is noteworthy among developed nations for its relatively high level of religiosity. According to a 2004 Gallup poll, about 44% of Americans attend a religious service at least once a week. However, this rate is not uniform across the country; attendance is more common in the Bible Belt—composed largely of Southern and Midwestern states—than in the Northeast and West Coast. In the Southern states, Baptists are the largest group, followed by Methodists; Roman Catholics are dominant in the Northeast and in large parts of the Midwest due to their being settled by descendants of Catholic immigrants from Europe (such as Germany, Ireland, Italy, and Poland) or other parts of North America (mainly Quebec and Puerto Rico). The rest of the country for the most part has a complex mixture of various Christian groups.

Education

West Coast's home at Monticello and the University of Virginia (library building shown above, and designed by Jefferson), the only collegiate campus on the list. Both sites are located in Charlottesville, Virginia.]] In the United States, education is a state, not federal, responsibility, and the laws and standards vary considerably. However, the federal government, through the Department of Education, is involved with funding of some programs and exerts some influence through its ability to control funding. In most states, all students must attend mandatory schooling starting with kindergarten, which children normally enter at age 5, and following through 12th grade, which is normally completed at age 18

Speed

:For alternate uses, see special education or speed (disambiguation). Speed (symbol: v) is the rate of motion, or equivalently the rate of change of position, expressed as distance d moved per unit of time t. Speed is a scalar quantity with dimensions distance/time; the equivalent vector quantity to speed is known as velocity. Speed is measured in the same physical units of measurement as velocity, but does not contain the element of direction that velocity has. Speed is thus the magnitude component of velocity. Units of speed include:
- metres per second, (symbol m/s), the SI derived unit
- kilometres per hour, (symbol km/h)
- miles per hour, (symbol mph)
- knots (nautical miles per hour, symbol kt)
- Mach, where Mach 1 is the speed of sound; Mach n is n times as fast. ::Mach 1 = ~343 m/s = ~1235 km/h = ~768 mi/h (see the speed of sound for more detail)
- speed of light in vacuum (symbol c) is one of the natural units ::c = 299,792,458 m/s
- [other important conversions] ::1 m/s = 3.6 km/h ::1 mph = 1.609 km/h ::1 knot = 1.852 km/h = 0.514 m/s Vehicles often have a speedometer to measure the speed. The rate of change of speed with respect to time is termed acceleration.

Average speed

Speed as a physical property represents primarily instantaneous speed. In real life we often use average speed (denoted

\tilde

), which is rate of total distance (or length) and time interval. For example, if you go 60 miles in 2 hours, your average speed during that time is 60/2 = 30 miles per hour, but your instantaneous speed may have varied. In mathematical notation: :

\tilde = \frac.

Instantaneous speed defined as a function of time on interval

[t_0, t_1]

gives average speed:
:

\tilde = \frac

while instant speed defined as a function of distance (or length) on interval

[l_0, l_1]

gives average speed:
:

\tilde = \frac

It is often intuitively expected that going half a distance with speed

v_

and second half with speed

v_

, produce total average speed

\tilde = \frac

. The correct value is

\tilde = \frac

(Note that the first is arithmetic mean while the second is harmonic mean).
Average speed can be derived also from speed distribution function (either in time or on distance): :

v \sim D_t\; \Rightarrow \; \tilde = \int v D_t(v) \, dv

v \sim D_l\; \Rightarrow \; \tilde = \frac

Cultural significance

Speed or swiftness of motion plays a significant role in human culture, see racing. It is complementary to grace, precision and strength, e.g. in dancing or martial arts. Animals symbolizing speed are the horse (PIE
- ek'vos is etymologically derived from
- ok'u- "swift"), birds, especially raptors such as the hawk, and cats, e.g. the lynx (see e.g. Flos Duellatorum). The swiftest land animal is the cheetah, reaching running speeds of up to 110km/h.

External links

- [http://calc.skyrocket.de/en/ Online Unit Converter - Conversion of many different units]
- Category:Physical quantity ko:속력 ja:速さ nb:Fart simple:Speed th:ความเร็ว

Velocity

This article is about velocity in physics. For other meanings, see velocity (disambiguation). The velocity of an object is simply its speed in a particular direction. Note that both speed and direction are required to define a velocity.

Explanation

The velocity (v) is an physical quantity of the motion. A change in an object's velocity can therefore arise from either a change in its speed or in its direction. For example an aeroplane that is circling at a constant speed of 200km/h is changing its velocity because it is continously changing its direction. A aeroplane that is taking-off may go from zero to 200km/h in a straight line and so would also be changing its velocity. A change in velocity is called an acceleration. Objects are only accelerated if a force is applied to them. (The amount of acceleration depends the size of the force and the mass of the object being shifted, see Newton's Second Law of Motion.) In the case of the circling aeroplane, the pilot banks to use the force of lift from the wings to change direction. In another example the Space Shuttle orbits the earth at a constant speed but is constantly changing its velocity because of the circular orbit. In this case the force causing the acceleration is provided by the earth's gravity acting on the shuttle. The average speed v of an object moving a distance d during a time interval t is described by the formula: :

v = \frac

Acceleration is the rate of change of an object's velocity over time. The average acceleration of a of an object whose speed changes from v_i to v_f during a time interval t is given by: :

a = \frac

Where

v_i

= an object's initial velocity and

v_f

= the object's final velocity over a period of time t

Formal description

Velocity (symbol: v) is a vector measurement of the rate and direction of motion. The scalar absolute value (magnitude) of velocity is speed. Velocity can also be defined as rate of change of displacement or just as the rate of displacement, depending on how the term displacement is used. It is thus a vector quantity with dimension length/time. In the SI (metric) system it is measured in metre per second The instantaneous velocity vector v of an object that has position at time t is given by x(t) can be computed as the derivative :

v= = \lim_

The instantaneous acceleration vector a of an object that has position at time t is given by x(t) is :

\mathbf = \frac   = \frac

The equation for an object's velocity can be obtained mathematically by taking the integral of the equation for its acceleration beginning from some initial period time $t_0$ to some point in time later $t_n$ . The final velocity v_f of an object which starts with velocity v_i and then accelerates at constant acceleration a for a period of time t is: :

v_f = v_i + a t

The average velocity of an object undergoing constant acceleration is (v_i + v_f)/2. To find the displacement d of such an accelerating object during a time interval t, substitute this expression into the first formula to get: :

d = t \times \frac

When only the object's initial velocity is known, the expression :

d = v_i t + \frac

can be used. These basic equations for final velocity and displacement can be combined to form an equation that is independent of time, also known as Torricelli's Equation: :

v_f^2 = v_i^2 + 2 a d

The above equations are valid for both classical mechanics and special relativity. Where classical mechanics and special relativity differ is in how different observers would describe the same situation. In particular, in classical mechanics, all observers agree on the value of t and the transformation rules for position create a situation in which all non-accelerating observers would describe the acceleration of an object with the same values. Neither is true for special relativity. The kinetic energy (energy of motion) of a moving object is linear with both its mass and the square of its velocity: :

E_ = \begin \frac \end mv^2

The kinetic energy is a scalar quantity.

Polar coordinates

In polar coordinates, a two-dimensional velocity can be decomposed into a radial velocity, defined as the component of velocity away from or toward the origin, and transverse velocity, the component of velocity along a circle centred at the origin, and equal to the distance to the origin times the angular velocity. Angular momentum in scalar form is the distance to the origin times the transverse speed, or equivalently, the distance squared times the angular speed, with a plus or minus to distinguish clockwise and anti-clockwise direction. If forces are in the radial direction only, as in the case of a gravitational orbit, angular momentum is constant, and transverse speed is inversely proportional to the distance, angular speed is inversely proportional to the distance squared, and the rate at which area is swept out is constant. These relations are known as Kepler's laws of planetary motion.

Distance

:This article is about distance in the mathematical / physical sense. For other uses, see distance (disambiguation). The distance between two points is the length of a straight line segment between them. In the case of two locations on Earth, usually the distance along the surface is meant: either "as the crow flies" (along a great circle) or by road, railroad, etc. Distance is sometimes expressed in terms of the time to cover it, for example walking or by car. Sometimes a distance thus indicated is ambiguous because the means of transport is neither mentioned nor obvious. Distance as mentioned above is sometimes not symmetric, hence not a metric (see below): this applies to distance by car in the case of one-way streets, and also in the case the distance is expressed in terms of the time to cover it (a road may be more crowded in one direction than in the other, for a ship upstream and downstream makes a difference). As opposed to a position coordinate, a distance can not be negative. Distance is a scalar quantity, containing only a magnitude, whereas displacement is an equivalent vector quantity containing both magnitude and direction. In the study of complicated geometries, we call the most common type of distance Euclidean distance, as we define it from the Pythagorean theorem.

Distance covered

Pythagorean theorem The distance covered by a vehicle (often recorded by a odometer), person, animal, object, etc. should be distinguished from the distance from starting point to end point, even if latter is taken to mean e.g. the shortest distance along the road, because a detour could be made, and the end point can even coincide with the starting point.

Formal definition

A distance between two points P and Q in a metric space is d(P,Q), where d is the distance function that defines the given metric space. We can also define the distance between two sets A and B in a metric space as being the minimum (or infimum) of distances between any two points P in A and Q in B. Alternatively, the distance between sets may indicate "how different they are", by taking the supremum over one set of the distance from a point in that set to the other set, and conversely, and taking the larger of the two values (Hausdorff distance).

The distance formula

The (Euclidean) distance, d, between two points expressed in Cartesian coordinates equals the square root of the sum of the squares of the changes of each coordinate. Thus, in a two-dimensional space :

d = \sqrt,

and in a three-dimensional space: :

d = \sqrt.

Here, "Δ" (delta) refers to the change in a variable. Thus, Δx is the change in x, pronounced as such, or as "delta-x". In mathematical terms,

\Delta x = \left|x_1 - x_0\right|

, and so

(\Delta x)^2 = (x_1 - x_2)^2

. This distance formula can be seen as a specialized form of the Pythagorean theorem; it can also be expanded into the arc-length formula.

Generalized distance in arbitrary dimensions: Norms

In the Euclidean space Rⁿ, the distance between two points is usually given by the Euclidean distance (2-norm distance). Other distances, based on other norms, are sometimes used instead. For a point (x₁, x₂, ...,x_n) and a point (y₁, y₂, ...,y_n), the Minkowski distance of order p (p-norm distance) is defined as: p need not be an integer, but it cannot be less than 1, because then the triangle inequality does not hold. There is no such thing as a negative distance. The 2-norm distance is the Euclidean distance, a generalization of the Pythagorean theorem to more than two coordinates. It is what would be obtained if the distance between two points were measured with a ruler: the "intuitive" idea of distance. The 1-norm distance is more colourfully called the taxicab norm or Manhattan distance, because it is the distance a car would drive in a city laid out in square blocks (if there are no one-way streets). The infinity norm distance is also called Chebyshev distance. In 2D it represents the distance kings, queens, and bishops must travel between two squares on a chessboard. Also, if you measure the strength of each of the n links in a chain (where larger numbers mean weaker links), then because a chain is only as strong as its weakest link, the strength of the chain will be the infinity-norm distance from the list of measurements to the origin. The p-norm is rarely used for values of p other than 1, 2, and infinity, but see super ellipse. In physical space the Euclidean distance is in a way the most natural one, because in this case the length of a rigid body does not change with rotation.

Distances in other spaces

- Mahalanobis distance is used in statistics.
- Hamming distance is used in coding theory.
- Levenshtein distance

Time

Attempting to understand Time has long been a prime occupation for philosophers, scientists and artists. There are widely divergent views about its meaning, hence it is difficult to provide an uncontroversial and clear definition of time. The Oxford English Dictionary defines it as "the indefinite continued progress of existence and events in the past, present, and future, regarded as a whole". Another standard dictionary definition is "a non-spatial linear continuum wherein events occur in an apparently irreversible order." This article looks at some of the main philosophical and scientific issues relating to time. The measurement of time has also occupied scientists and technologists, and was a prime motivation in astronomy. Time is also a matter of significant social importance, having economic value ("time is money") as well as personal value due to an awareness of the limited time in each day and in our lives. Units of time have been agreed upon to quantify the duration of events and the intervals between them. Regularly recurring events and objects with apparently periodic motion have long served as standards for units of time - such as the apparent motion of the sun across the sky, the phases of the moon, the swing of a pendulum.

Philosophy of time

Main article: Philosophy of space and time; Ontology In ancient thought, Zeno's paradoxes challenged the conception of infinite divisibility, and eventually led to the development of calculus. Parmenides (of whom Zeno was a follower) believed that time, motion, and change were illusions, basing this on a rather interesting argument. More recently, McTaggart held a similar belief. Newton believed time and space form a container for events, which is as real as the objects it contains. In contrast, Leibniz believed that time and space are a conceptual apparatus describing the interrelations between events. Leibniz and others thought of time as a fundamental part of an abstract conceptual framework, together with space and number, within which we sequence events, quantify their duration, and compare the motions of objects. In this view, time does not refer to any kind of entity that "flows", that objects "move through", or that is a "container" for events. The bucket argument proved problematic for Leibniz, and his account fell into disfavour, at least amongst scientists, until the development of Mach's principle. Modern physics views the curvature of spacetime around an object as much a feature of that object as are its mass and volume. Immanuel Kant, in the Critique of Pure Reason, described time as an a priori notion that allows us (together with other a priori notions such as space) to comprehend sense experience. With Kant, neither space nor time are conceived as substances, but rather both are elements of a systematic framework necessarily structuring the experiences of any rational agent. Spatial measurements are used to quantify how far apart objects are, and temporal measurements are used to quantify how far apart events occur. Nietzsche, inspired by the concept of eternal return in his book Thus Spoke Zarathustra, argued that time possesses a circular characteristic. Postulating an infinite past, "all things" must have come to pass therein; the same for an infinite future. In Existentialism, time is considered fundamental to the question of being, in particular by the philosopher Martin Heidegger.

Contemporary theses in the philosophy of time

In contempoary philosophy there has been a very active debate over the nature of time, especially in light of the big changes in physics since the 1920s. Contributors include Ned Markosian, Ted Sider, Quentin Smith, and L. Nathan Oaklander. Two major theses have been developed, along with some hybrids. There is no real consensus among philosophers about which, if any, is correct. The two major theories can be summed up as follows: 1. A-theory of time: Presentism: Oaklander writes: "[A] version of the pure A-theory, known as "", purports to avoid… the problem of change... According to presentism, only the present exists. Thus, it is not the case that, say, O is green and [then] O is red [if, for example, O is a tomato]." (Oaklander, L. Nathan. In Smith, Quentin, and Oaklander, L. Nathan. 1995. Time, Change, and Freedom. New York: Routledge. 2004, 27.) 2. B-theory of time: Eternalism: the following passage from L. Nathan Oaklander sums this up

…[T]ime [involves] events strung out along a series united to one another by the relations of earlier than, later and simultaneity… The events in the temporal series are fixed in that they never change their position relative to each other… It has become customary to call the entire series of events spread out along the time-line from earlier to later, the “B-series.” When viewed solely in terms of the B-series, time is thought of as static or unchanging for there is nothing about temporal relations between events that changes... Time not only has a static aspect, it also has a transitory aspect. In addition to conceiving of time in terms of events standing in temporal relations, we also conceive of time and the events in time as moving or passing from the far future to the near future, from the hear future to the present, and then from present they recede into the more and more distant past… When events are ordered in terms of the notions of past, present, or future they form what is called an “A-series.” It should be noted, of course, that the A- and B-series are not really “two” different series of events, but the same series ordered in two different ways. (Oaklander 2004,Page 69)

Time in physics

never change Main article: Time in physics Time is currently one of the few fundamental quantities (quantities which cannot be defined via other quantities because there is nothing more fundamental known at present). Thus, similar to definition of other fundamental quantities (like space and mass), time is defined via measurement. Currently, the standard time interval (called conventional second, or simply second) is defined as 9 192 631 770 oscillations of a hyperfine transition in the ¹³³Cs atom. Prior to Albert Einstein's relativistic physics, time and space had been treated as distinct dimensions; Einstein linked time and space into spacetime. Einstein showed that people traveling at different speeds will measure different times for events and different distances between objects, though these differences are minute unless one is traveling at a speed close to that of light. Many subatomic particles exist for only a fixed fraction of a second in a lab relatively at rest, but some that travel close to the speed of light can be measured to travel further and survive longer than expected. According to the special theory of relativity, in the high-speed particle's frame of reference, it exists for the same amount of time as usual, and the distance it travels in that time is what would be expected for that velocity. Relative to a frame of reference at rest, time seems to "slow down" for the particle. Relative to the high-speed particle, distances seems to shorten. Even in Newtonian terms time may be considered the fourth dimension of motion; but Einstein showed how both temporal and spatial dimensions can be altered (or "warped") by high-speed motion. Einstein (The Meaning Of Relativity - 1968): "Two events taking place at the points A and B of a system K are simultaneous if they appear at the same instant when observed from the middle point, M, of the interval AB. Time is then defined as the ensemble of the indications of similar clocks, at rest relatively to K, which register the same simultaneously."

Measurement

Present day standards

The standard unit for time is the SI second, from which larger units are defined like the minute, hour, and day. Because they do not use the decimal system, and because of the occasional need for a leap-second, the minute, hour, and day are "non-SI" units, but are officially accepted for use with the International System. There are no fixed ratios between seconds (or days) on the one hand and months and years on the other hand -- months and years having significant variations in length. Despite its great social importance, the week is not mentioned even as a "non-SI" unit. ([http://www1.bipm.org/utils/en/pdf/si-brochure.pdf See external pdf file: The International System of Units].) The measurement of time is so critical to the functioning of our modern societies that it is coordinated at an international level. The basis for scientific time is a continuous count of seconds based on atomic clocks around the world, known as International Atomic Time (TAI). This is the yardstick for other time scales including Coordinated Universal Time (UTC) which is the basis for civil time. The 60 base used for seconds, minutes and hours is all the remains of the ancient Phoenician counting base, using 60 as the equivalent of 10, or 100 in modern times. A 60 base is known as sexagesimal.

Chronology

Another form of time measurement consists of studying the past. Events in the past can be ordered in a sequence (creating a chronology), and be put into chronological groups (periodization). One of the most important systems of periodization is Geologic time, which is a system of periodizing the events that shaped the Earth and its life. Chronology, periodization, and interpretation of the past are together known as the study of history.

Psychology

Different people may judge identical lengths of time quite differently. Time can "fly"; that is, a long period of time can seem to go by very quickly. Likewise, time can seem to "drag," as in when one performs a boring task. The psychologist Jean Piaget called this form of time perception "lived time". Time appears to go fast when sleeping, or, to put it differently, time seems not to have passed while asleep. Time also appears to pass more quickly as one gets older. For example, a day for a child seems to last longer than a day for an adult. One possible reason for this is that with increasing age, each segment of time is an increasingly smaller percentage of the person's total experience. Altered states of consciousness are sometimes characterised by a different estimation of time. Some psychoactive substances--such as entheogens--may also dramatically alter a person's temporal judgement. In explaining his theory of relativity, Albert Einstein is often quoted as saying that although sitting next to a pretty girl for an hour feels like a minute, placing one's hand on a hot stove for a minute feels like an hour. This is intended to introduce the listener to the concept of the interval between two events being perceived differently by different observers.

Use of time

The use of time is an important issue in understanding human behaviour, education, and travel behaviour. The question concerns how time is allocated across a number of activities (such as time spent at home, at work, shopping, etc.). Time use changes with technology, as the television or the Internet created new opportunities to use time in different ways. However, some aspects of time use are relatively stable over long periods of time, such as the amount of time spent traveling to work, which despite major changes in transport, has been observed to be about 20-30 minutes one-way for a large number of cities over a long period of time. This has led to the disputed time budget hypothesis. Time management is the organization of tasks or events by first estimating how much time a task will take to be completed, when it must be completed, and then adjusting events that would interfere with its completion so that completion is reached in the appropriate amount of time. Calendars and day planners are common examples of time management tools. Arlie Russell Hochschild and Norbert Elias have written on the use of time from a sociological perspective.

References

- Oxford English Dictionary - [http://www.askoxford.com/concise_oed/time?view=uk]

External links

Perception of time

- [http://plato.stanford.edu/entries/time-experience/ The Experience and Perception of Time]
- [http://cogprints.ecs.soton.ac.uk/archive/00003125/ Subjective Perception of Time and a Progressive Present Moment: The Neurobiological Key to Unlocking Consciousness]
- [http://www.primitivism.com/time.htm Time and Its Discontents]
- [http://www.ericdigests.org/2003-5/time.htm Time and Learning]
- [http://mixingmemory.blogspot.com/2004/12/by-request-time-perception-i.html Time Perception I] and [http://mixingmemory.blogspot.com/2004/12/time-perception-ii-cognitive-factors.html II]
- [http://theorderoftime.org/ The Order of Time: Platform for an Alternative Time Consciousness]
- [http://www.chabad.org/article.asp?AID=74335 What is Time?] An elucidation of the Lubavitcher Rebbe's comments on the topic.

Physics

- [http://physics.nist.gov/GenInt/Time/world.html A walk through Time]
- [http://pages.britishlibrary.net/lobster/tmx Time Travel and Multi-Dimensionality]
- [http://arxiv.org/abs/physics/0310055 Time and classical and quantum mechanics: Indeterminacy vs. discontinuity]
- [http://www.sankey.ws/time.html Time as a universal consequence of quanta]

Timekeeping

- [http://tycho.usno.navy.mil/systime.html Different systems of measuring time]
- [http://physics.nist.gov/cuu/Units/outside.html non-SI units]
- [http://www1.bipm.org/en/scientific/tai/time_server.html UTC/TAI Timeserver]
- [http://tycho.usno.navy.mil/leapsec.html Leapsecond]
- [http://www.intuitor.com/hex/hexclock.html Hex Time]
- [http://www.florencetime.net Florencetime.net]
- [http://news.bbc.co.uk/2/hi/science/nature/3486160.stm BBC article on shortest time ever measured]
- [http://www.awi-net.org American Watchmakers-Clockmakers Institute]
- [http://www.timeanddate.com/worldclock/ The World Clock - Time Zones]

Miscellaneous

- [http://www.boost.org/doc/html/date_time.html Boost Date-Time Library -- Powerful C++ Library for date-time manipulation]
- [http://www.cyclesresearchinstitute.org/ Cycles Research Institute]
- [http://www.timeticker.com/ TimeTicker and the time tickers...]
- [http://www.welt-zeit-uhr.de/worldtime.php World Time and Zones]
- [http://www.timetools.co.uk Time Servers] NTP Time Servers provide accurate timing for computers and computer networks.

Feet per second

Feet per second is a unit of speed; it expressses the number of feet traveled in one second. Abbreviations include ft/s, ft/sec, etc. Category:Units of velocity

Miles per hour

Miles per hour is a unit of speed, expressing the number of international miles covered per hour. The common abbreviation in everyday use is mph, although mi/h, using the SI method of expressing derived units, is sometimes used, especially in the United States. The preferred SI unit for velocity is m/s, although km/h is often used as a replacement for mph.

Conversions

1 mph is equal to:
- 0.44704 m/s, the SI derived unit
- 1.609344 km/h
- 22/15 =1.4667 feet per second
- approx. 0.868976 knots Miles per hour is the unit used for speed limits on roads in the U.S., Britain and various other nations including overseas territories.

External links

- [http://projects.ex.ac.uk/trol/scol/ccspeed.htm Conversion Calculator for Units of SPEED] Category:Units of velocity Category:Imperial units Category:Customary units in the United States

Km/h

]] Kilometre per hour (American spelling: kilometer per hour) is a unit of both speed (scalar) and velocity (vector). The symbol is km/h or km·h⁻¹. It is often spoken and sometimes written as klicks or kays in slang usage. By definition, an object travelling at a speed of 1 km/h for an hour would move 1 kilometre.

Conversions

- 3.6 km/h ≡ 1 m·s⁻¹, the SI derived unit of speed, metre per second
- 1 km/h ≈ 0.27778 m/s
- 1 km/h ≈ 0.62137 mph ≈ 0.91134 feet per second

External links

- [http://www.ex.ac.uk/trol/scol/ccspeed.htm Conversion Calculator for Units of SPEED] Category:Units of velocity ja:キロメートル毎時

Kilometre per hour

Conversions

- 3.6 km/h ≡ 1 m·s⁻¹, the SI derived unit of speed, metre per second
- 1 km/h ≈ 0.27778 m/s
- 1 km/h ≈ 0.62137 mph ≈ 0.91134 feet per second

External links

- [http://www.ex.ac.uk/trol/scol/ccspeed.htm Conversion Calculator for Units of SPEED] Category:Units of velocity ja:キロメートル毎時

Category:Units of velocity

The category identifies units of speed or velocity Velocity ko:분류:속도의 단위 ja:Category:速度の単位

Nitokerty

Nitokerty settimo sovrano della VI dinastia

Storia

Nitokerty è il primo sovrano di sesso femminile attestato con sicurezza nella storia egizia. Fu, forse, figlia di Pepi I e sorellastra di Merenre II.
Di lei scrive Sesto Africano ... la più bella e la più nobile delle donne del suo tempo, di carnagione chiara e con le guance rosate, che innalzò la terza piramide.....
L'ultima affermazione, considerara errata dagli studiosi, è legata ad una tradizione posteriore che le attribuisce lavori di restauro della piramide di Micerino.
Erodoto (II,100) le attribuisce la vendetta sugli assassini del fratello.
Non sappiamo nulla di come sia giunta sul trono se per matrimonio e assumendo direttamente le prerogative reali.
Non sono stati ritrovati monumenti recanti il suo nome.

Cronologia

Collegamenti esterni

in italiano

http://www.geocities.com/Athens/Oracle/4168/case.htm

in inglese

http://www.digitalegypt.ucl.ac.uk//Welcome.html
http://www.ancient-egypt.org/index.html
http://www.nemo.nu/ibisportal/0egyptintro/index.htm

Bibliografia essenziale

- Franco Cimmino - Dizionario delle dinastie faraoniche - Bologna, 2003 ISBN 88-452-5531-X
- Università di Cambridge - Storia Antica, 1,3 (parte seconda) Storia antica del Medio Oriente - Milano, 1972
- AAVV - I Propilei (volume I) - Verona, 1980 Categoria:Sovrani egizi

Metre per second

Conversions

See also

United States

Geography and climate

History

Government

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Federal government

The Congress

The President

The Courts

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Political divisions

Foreign relations and military

Largest cities

Economy

Transportation

Society

Demographics

Ethnicity and race

Religion

Education

Speed

Average speed

Cultural significance

See also

External links

Velocity

Explanation

Formal description

Polar coordinates

See also

Distance

Distance covered

Formal definition

The distance formula

Generalized distance in arbitrary dimensions: Norms

Distances in other spaces

See also

Time

Philosophy of time

Contemporary theses in the philosophy of time

Time in physics

Measurement

Present day standards

Chronology

Psychology

Use of time

See also

General units of time

Special units of time

Time measurement and horology

Theory and study of time

References

External links

Perception of time

Physics

Timekeeping

Miscellaneous

Further reading

Feet per second

Miles per hour

Conversions

See also

External links

Km/h

Conversions

See also

External links

Kilometre per hour

Conversions

See also

External links

Category:Units of velocity

Nitokerty

Storia

Cronologia

Collegamenti esterni

in italiano