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A simple machine is a mechanical device that changes the direction or magnitude of a force. [1] In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. [2] Usually the term refers to the six classical simple machines that were defined by Renaissance scientists: [3] [4 ...
Teaching machines were originally mechanical devices that presented educational materials and taught students. They were first invented by Sidney L. Pressey in the mid-1920s. [1] His machine originally administered multiple-choice questions. The machine could be set so it moved on only when the student got the right answer.
The hand axe is the first example of a wedge, the oldest of the six classic simple machines, from which most machines are based. The second oldest simple machine was the inclined plane (ramp), [6] which has been used since prehistoric times to move heavy objects. [7] [8] The other four simple machines were invented in the ancient Near East. [9]
On the 500th anniversary of the Spanish conquest of the Aztecs in Mexico, on Aug. 13, 1521, the documentary "499" from Rodrigo Reyes tackles colonialism's shadow.
The screw, the last of the simple machines to be invented, [12] first appeared in Mesopotamia during the Neo-Assyrian period (911–609) BC. [11] According to the assyriologist Stephanie Dalley , the earliest pump was the screw pump , first used by Sennacherib , King of Assyria , for the water systems at the Hanging Gardens of Babylon and ...
Two out of the four schools of Islamic law, i.e. Hanafi and Maliki schools, accepted non-Arab polytheists to be eligible for the dhimmi status. Under this doctrine, Arab polytheists were forced to choose between conversion and death. However, according to perception of most Muslim jurists, all Arabs had embraced Islam during the lifetime of ...
Spear-armed hoplite from Greco-Persian Wars. A spear is a polearm consisting of a shaft, usually of wood, with a pointed head.The head may be simply the sharpened end of the shaft itself, as is the case with fire hardened spears, or it may be made of a more durable material fastened to the shaft, such as bone, flint, obsidian, copper, bronze, iron, or steel.
The Ottomans ended the Eastern Roman Empire with the conquest of Constantinople in 1453 by Mehmed the Conqueror. [8] Expansion of the Tsardom of Russia from 1547 to 1725. The militarist and nationalistic reign of Russian Czar Nicholas I (1825–1855) led to wars of conquest against Persia (1826–1828) and Turkey (1828–1829).