Photo: The US Navy's largest helicopter: the CH53-E Sikorsky Super Stallion. A newer version, the CH-53K, is currently under development and expected to cost about $100 million per helicopter! Picture by Joshua Adam Nuzzo courtesy of US Navy .

The science of a helicopter is exactly the same as the science of an airplane : it works by generating lift—an upward-pushing force that overcomes its weight and sweeps it into the air. Planes make lift with airfoils (wings that have a curved cross-section). As they shoot forwards, their wings change the pressure and direction of the oncoming air, forcing it down behind them and powering them up into the sky: a plane's engines speed it forward, while its wings fling it up. The big problem with a plane is that lots of air has to race across its wings to generate enough lift; that means it needs large wings, it has to fly fast, and it needs a long runway for takeoff and landing.

Photo: Right: Mighty rotors: You can see just how big and heavy a helicopter's rotors are in this picture. It takes four US marines to hold this rotor in place while it's being reattached after maintenance. Notice the curved front edge of the rotor blade that cuts like an airfoil as it spins around. Picture by Jeremy L. Grisham courtesy of US Navy .

Photo: The US Navy's largest helicopter: the CH53-E Sikorsky Super Stallion. A newer version, the CH-53K, is currently under development and expected to cost about $100 million per helicopter! Picture by Joshua Adam Nuzzo courtesy of US Navy .

The science of a helicopter is exactly the same as the science of an airplane : it works by generating lift—an upward-pushing force that overcomes its weight and sweeps it into the air. Planes make lift with airfoils (wings that have a curved cross-section). As they shoot forwards, their wings change the pressure and direction of the oncoming air, forcing it down behind them and powering them up into the sky: a plane's engines speed it forward, while its wings fling it up. The big problem with a plane is that lots of air has to race across its wings to generate enough lift; that means it needs large wings, it has to fly fast, and it needs a long runway for takeoff and landing.

Photo: Right: Mighty rotors: You can see just how big and heavy a helicopter's rotors are in this picture. It takes four US marines to hold this rotor in place while it's being reattached after maintenance. Notice the curved front edge of the rotor blade that cuts like an airfoil as it spins around. Picture by Jeremy L. Grisham courtesy of US Navy .

The Renaissance ( UK : / r ɪ ˈ n eɪ s ən s / , US : / r ɛ n ə ˈ s ɑː n s / ) [1] was a period in European history , from the 14th to the 17th century, regarded as the cultural bridge between the Middle Ages and modern history . It started as a cultural movement in Italy in the Medieval period and later spread to the rest of Europe, marking the beginning of the Modern age .

The intellectual basis of the Renaissance was its own invented version of humanism , derived from the concept of Roman Humanitas and the rediscovery of classical Greek philosophy, such as that of Protagoras , who said that "Man is the measure of all things." This new thinking became manifest in art, architecture, politics, science and literature. Early examples were the development of perspective in oil painting and the recycled knowledge of how to make concrete . Although the invention of metal movable type sped the dissemination of ideas from the later 15th century, the changes of the Renaissance were not uniformly experienced across Europe.

The Renaissance began in Florence , in the 14th century. [4] Various theories have been proposed to account for its origins and characteristics, focusing on a variety of factors including the social and civic peculiarities of Florence at the time: its political structure; the patronage of its dominant family, the Medici ; [5] [6] and the migration of Greek scholars and texts to Italy following the Fall of Constantinople to the Ottoman Turks . [7] [8] [9] Other major centres were northern Italian city-states such as Venice , Genoa , Milan , Bologna , and finally Rome during the Renaissance Papacy .

The World of Leonardo: 1452-1519: Amazon.co.uk: Robert.


World of Leonardo: Robert Wallace. - amazon.com

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