Actually my objection is to your shortening of the statement.
ok, i want to claim that "only force accelerates", contains all the information of the original statement, plus some more information, which makes it better definition. i want to claim that this short statement can substitute the original statement, completely and in every case.
And there is no circular motion at constant velocity, by definition — velocity is a vector.
i agree definition is such, i was referring that to lead these two statements in contradiction:
1.) when light bends due to gravity, it does not accelerate - it follows curvature of space-time
2.) magnetic field can not accelerate charged particles, but still it can change their direction
"uniform motion" is defined, and not ambiguous
i agree. it is explained, that if you read original text you may notice that he means constant velocity as well as constant acceleration. but when making new, modern formulation why not make it crystal clear. why not call "change in motion" - acceleration, we have a name for it, why not use it? why make it confusing? whats the point of words "tend", "external", "unbalanced"?
the sentence does not have "focus", its hard to see what is it about and why is it important. it kind of tries to be about "frames of reference" while it can not be about anything else but the force, since the "force" is a 'primary' word needing description.
In regard to the OP, I suspect the word "tend" may have some ties to the notion that Newton displaced, which was that an object's natural tendency was to come to rest, i.e. that was a dynamic thing. Moving objects tend to come to rest. The translation of Newton is saying that no, it's only objects already at rest that tend to remain that way, and they do not start to move on their own, i.e. there is no tendency for spontaneous motion: motion from a state of rest requires a force.
word "tend" has no place in there, it gives no explanation for anything , it only makes statement more undefined. it makes you feel as if there is some threshold to which object resist to change motion.
it is as if some more inert objects will not react at all, it makes you think that some minimal force will produce no effect what so ever, or that is a matter of chance.
definition should use words like: all, none, never, always, only...
...Galileo realized that force acting on a body determines acceleration, not velocity. This insight leads to Newton's First Law—no force means no acceleration, and hence the body will maintain its velocity.
this sums up my line of thought
Edited by PlayStationX, 13 January 2009 - 07:31 PM.