The word "parachute" comes from "para", meaning "against" or "counter" in Ancient Greek, and "chute", the French word for "fall". In many other languages, the word refers to "falling-screen", such as German "Fallschirm". Some modern parachutes are classified as semi-rigid wings, which are maneuverable and can make a controlled descent to break on impact with the ground.
The inventor Leonardo Da Vinci sketched a parachute in his "Codex Atlanticus" (fol. 381v), in about 1485. Leonardo's canopy was held open by a square wooden frame. The feasibility of Leonardo's pyramidal design was successfully tested in 2000 by the Briton Adrian Nicholas and again in 2008 by another skydiver. According to the historian of technology Lynn White, these conical and pyramidal designs, much more elaborate than early artistic jumps with rigid parasols in Asia, mark "the origin of the parachute as we know it".
The parachute package is called "rig". It consists of backpack, harness and canopy. The backpack is the container in which the parachute is stored, and which opens up when the parachute is deployed. The harness is the strapping on which the backpack is attached to the jumper. Modern harnesses have leg straps, vertical (upwards) straps and chest strap which can be tightened snug. The fabric part of the parachute is called "canopy". It is attached to the harness by lines, which themselves attach to four straps called "risers". The canopy may be round, bell-like, resembling like a jellyfish, or the canopy may be a mattress-like, resembling a wing profile. Most army parachutes are bell parachutes, while most recreational, rescue and professional parachutes are wing parachutes.
Usually the backpack contains not just one but two parachutes: "main" parachute, which is opened normally, and "reserve" parachute, which is opened in an emergency situation, such as when the main does not open or is tangled. The use of reserve parachute have saved thousands of jumpers who would otherwise have died.
Old-fashioned bell parachutes were opened by pulling a rip cord. Modern parachutes do not have rip cords anymore, but the skydiver simply throws a small auxiliary (helper) parachute called "pilot chute" into air. This small auxiliary chute then pulls the main parachute canopy out of its pod in the backpack and it inflates (fills with air) automatically.
A parachute is carefully folded, or "packed" to ensure that it will open reliably. If a parachute is not packed properly it may result in death since the main parachute might fail to deploy (open and develop) correctly or fully. In the U.S. and many developed countries, emergency and reserve parachutes are packed by "riggers" who must be trained and certified according to legal standards. Sport skydivers are always trained to pack their own primary "main" parachutes. Many skydivers never let anyone else to pack their parachutes because they know the rig is correctly packed when they have done it themselves.
Parachutes can malfunction in several ways. Malfunctions can range from minor problems that can be corrected in-flight and still be landed, to catastrophic malfunctions that require the main parachute to be cut away using a modern 3-ring release system, and the reserve be deployed. Most skydivers also equip themselves with small barometric computers (known as an AAD or automatic activation device like Cypres, FXC or Vigil) that will automatically activate the reserve parachute if the skydiver has not deployed a parachute to reduce his rate of descent by a preset altitude.
United States Capitol
The United States Capitol is the building where the United States Congress meets. It is the center of the legislative branch of the U.S. federal government. It is in Washington, D.C., on top of Capitol Hill at the east end of the National Mall.
The capitol has a large dome in the center, above a rotunda—a large space that is shaped like a circle. There are two "wings" that are connected to the rotunda on opposite sides. The north wing is where the Senate meets and the south wing is where the House of Representatives meets. These wings are also called "chambers". On the top floors of the chambers are "galleries", or balconies where people can watch the Senate and House of Representatives from above.
The Statue of Freedom is on top of the capitol.
The first capital city of the United States was New York City. At this time, Congress met in City Hall (Federal Hall) from 1785 to 1790. When the capital was moved to Philadelphia, Pennsylvania, from 1790 to 1800, the Philadelphia County Building (Congress Hall) became the capitol. In 1800, the capital moved again to Washington, D.C., and a new capitol building was built.
The capitol was designed by William Thornton. Construction started in 1793, but it was not completely finished until almost twenty years later. The Senate started to meet in the capitol in 1800, when the Senate wing was finished. The House started to meet in the capitol in 1807, even though the House wing was not finished until 1811.
At that time, it was not as big as it is now. The dome in the center of the building was smaller and made of wood. In 1814, the capitol was set on fire by the British Army during the War of 1812. In the 1850s and 1860s, the capitol was fully repaired, and the wooden dome was replaced with a larger iron dome. The walls of the Senate wing were painted with many murals about events in American History. Inside the rotunda, a large fresco was also painted on the ceiling during the repair.
The Supreme Court also met in the Capitol until its own building was completed in 1935.
The Capitol Dome is 8,909,200 pounds (4,009 tonnes) of cast-iron with 108 windows, and was constructed between 1855 and 1866.
On January 6, 2021, supporters of US President Donald Trump stormed into the capitol. This caused a lockdown in the building.
Strut bar
A car's strut bar or strut brace is to prevent body roll by bracing the top of the strut towers together.
Front-wheel drive
Front-wheel drive, or FWD, is a car setup, where the car's power is at the front wheels. This makes the car safe in wet and snowy conditions, because it has better traction, or grip, to the road. But, FWD can cause uneven weight, which may cause brakes to fail if used for large periods of time.
Rear-wheel drive
Rear-wheel drive, or RWD, is when a car uses its rear wheels to move. This is good for dry roads, and for acceleration, or how fast you move forward, as the weight is pushed backwards on the back wheels. But, RWD cars can spin out, also called oversteer or fishtail. This can cause crashes if the driver is new and not familiar with RWD cars.
Wireless
The word wireless is used to refer to any type of electrical or electronic operation which is done without a "hard wired" connection. Wireless communication is the transfer of information over a distance without the use of wires. The distances involved may be short (when using a television remote control) or very long (thousands or even millions of kilometers for radio communications).
One of the most popular wireless technology is the mobile phone, with more than 6.8 billion subscriptions worldwide as of 2013. The term wireless technology is generally used for mobile information technology (IT) equipment. Examples include mobile phones, personal digital assistants (PDAs), Global Positioning System (GPS) units, garage door openers, wireless computer mice and keyboards, satellite television and cordless telephones.
The world's first wireless telephone conversation happened in 1880, when Alexander Graham Bell and Charles Sumner Tainter invented photophone, a telephone that made conversations wirelessly using light beams. In 1946, a driver in Saint Louis, Mo. placed the first cell phone call in history. The cell phone was invented by Bell Labs and future AT&T CEO, H.I Romnes.
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