Ok since we talking about menchanics that we still have a minute let tell about ancient greek and what they call about menchanic it came up with the system for them seem to describe and explain different motion of different mate rial morth than 2 thousand years ago aritotle tha ancient greek philosopher assure that all matter on the earth was made up of four prime substances earth water air and fire under this system earth is denset water is next air is next fire is the last the heaviest objects were made of earth and water and lighter object contains significant amount of air or fire sowhen aristotle observe that different types of matter had different characteristic he assure that this is because different types were composed of different amouts of the four primary substances and aristotle believe that the motion of objects could be explained by basic natures of the four primary substances aristotle noticed that when he release most objects they would drop downward , but he also knew something would rise upward like smoke aristotle consider an object down and up to be a dominant nature of object so accroding to aristotle matter of rock were primarily composed by the earth 5 F1 J/ \# H5 x0 |* M( v
感觉 最近听力怎么不行了
