Safety equipment of bicycles

The bicycling manual contains rules concerning the safety equipment of bicycles.

Constructing shapes (3D)

Building 3D shapes into a given cube mesh with the help of several views.

Satellite types

Satellites orbiting the Earth can be used for civilian or military purposes.

Farming techniques

Farming techniques evolved with the development of human civilization in the Middle Ages and the Modern Age.

Jamestown (17th century)

Jamestown, founded in 1607, was the first permanent English settlement on the east coast of North America.

Working-class district (19th century)

Typical working-class districts with unhealthy living conditions were built at the time of the Industrial Revolution.

Medieval dungeon

A wide variety of torture devices were in use in medieval dungeons.

Formation of hydrogen molecules

Hydrogen atoms within hydrogen molecules are held together by a covalent bond.

Torii (gateway) of the Itsukushima Shrine

The torii is a traditional Japanese gate built at the entrance of shrines.

Viking longship (10th century)

These excellent shipbuilders and sailors traveled great distances on the seas and rivers.

Soap

Fatty acid molecules consist of a polar head and a non-polar tail, therefore they are suitable for removing fat stains.

Cannon operation (18th century)

The cannon was an important type of firearms at the beginning of modern history, widespread both on land and water.

Venice in the Middle Ages

Medieval Venice owed its wealth to its flourishing maritime trade.

Chlorination of methane by a substitution reaction

During the substitution reaction the hydrogen atoms of methane are substituted with chlorine atoms, the by-product is hydrogen chloride.

Calcium carbonate (CaCO₃)

Limestone is a widely and diversely used material.

Medieval smithy

The work of smiths – one of the first professions in history – became even more important in the Middle Ages.

Olympia (5th century B.C.)

The Olympic Games, held in the town every 4th year after 776 B.C. made it one of the centers of ancient Greece.

3D Tangram

A special, 3D version of the well-known Chinese logical game.

Golden Gate Bridge (San Francisco, 1937)

The suspension bridge that stretches above the strait between San Francisco Bay and the Pacific Ocean was opened in 1937.

Archimedes’s military inventions (3rd century B.C.)

Archimedes was one of the most brilliant Greek scholars of ancient times, who made his mark with military inventions as well.

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