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Motion
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Aristotle's Idea of Motion:

Aristotle had little interest in a mathematical approach to his explanation of motion. It was more philosophical than physical. In his time there were thought to be four earthly elements (and one heavenly one), each of which had a natural position that it tended to attain. Earth, the heaviest, tended towards Earth's center; Water, lighter than Earth but heavier than Air looked to position between the two; Fire, the lightest, rose through the air. There were two kinds of motion - natural and violent. When the elements sought their natural place (rocks sinking in water) the motion was natural. When the natural order was disturbed (a rock thrown through the air) the motion was violent and a force was required to maintain the violent motion. The rate at which motion occurred depended on the material (and in the case of violent motion, on the force). This led to some interesting and difficult to explain situations:

On falling bodies:
    Objects fall at a speed determined by their weight, and reach this speed alm