Newton 's Theory Of Motion Essay

2518 Words Jan 27th, 2015 null Page
It is sometimes argued that Newton 's first law of motion is tantamount to a definition of an inertial frame, or alternatively of a force-free body, and that the second law is just a definition of force. What is the flaw, if any, in these claims that neither law has any empirical content?

“Law I: Every body continues in its state of rest, or of uniform motion, in a right line, unless it is compelled to change that state by forces impressed upon it
“Law II: The change of motion is proportional to the motive force impressed; and is made in the direction of the straight line in which that force is impressed” (Newton, Principia, 1687)

Above is one of the more famous assertions of Newton’s first two laws of motion. In this essay I shall focus firstly on Newton’s motivation for the above claims, expanding on how they fit into his scientific framework. After we have seen how they fit into the Newtonian picture, we will then turn our gazes to the question of what content they could possibly have.
Newton imagined, to use an analogy given by Barbour, that space can be thought of as a medium stretching from infinity to infinity. Of course this medium is only conceptual, for objects pass through it entirely unimpeded. Similarly, Newton thought of time as ‘from its own nature… equably without relation to anything external’. This is of course in contrast to relationalists such as Leibniz who saw space and time as simply the totality of spatial and temporal relations between objects and…

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