hey guys i had a doubt can someone please explain me why force=mass x acceleration?
F=ma is sometimes looked at as a definition (especially by mathematicians), where it constitutes the definition of force based on measurable quantities mass and acceleration. But according to Thornton and Marion, really when Newton stated this, he meant something physical. I think what Newton really meant, more specifically, was that from an inertial reference frame, objects continue in straight lines unless acted upon by a net force--but the concept of an inertial reference frame isn't defined when you begin to state Newton's laws--so it's kind of a built-in assumption that's hard to avoid. That's why the mathematicians just ignore the physical meaning and take it as a definition.Every body continues in its state of rest or uniform motion in a straight line, except insofar as it doesn't.
Your view is certainly a valid way of looking at things, but it is not the only possible way.The reasoning presented here, viz., that the First and Second Laws are actually definitions and that the Third Law contains the physics, is not the only possible interpretation. Lindsay and Margenau (Li36), for example, present the first two Laws as physical laws and then derive the Third Law as a consequence.
This is not how Newton gave them. See http://en.wikisource.org/wiki/The_M...l_Philosophy_(1846)/Axioms,_or_Laws_of_MotionUsually Newton's first law is considered to be a definition of inertial frames and Newton's second law is considered to be a definition of forces. Once those terms are defined, then Newton's third law is the one that contains the actual physics.
This repeats Newton's own words almost verbatim! In the scholium that follows the Laws, he refers to multiple experiments, particularly by Galileo, that had established these laws.I'm sure the answer is that it's an empirical law. If you apply double the force, you observe the object accelerates twice as much. Do this experiment in enough ways and it's soon fairly convincing that F=ma and not m/a or ma^2 or something weird.
Excellent, then it seems we are not at odds.Your view is certainly a valid way of looking at things
Which is why I qualified my statements with the word "usually".but it is not the only possible way.
The problem is: How do we know that we've doubled the force? How else do we measure the force except using [itex]F = kma[/itex] itself? In other words, we're brought back to regarding [itex]F = kma[/itex] as true by definition.I'm sure the answer is that it's an empirical law. If you apply double the force, you observe the object accelerates twice as much. [... ]
This was extensively discussed in earlier threads, such as:hey guys i had a doubt can someone please explain me why force=mass x acceleration?
Experimental prototypes of force are not nearly as reliable as measurements of acceleration or experimental prototypes of mass. So generally it is preferable to take Newton's 2nd as a definition of force, since you can get more accurate results that way than by using an experimental prototype force. Your rather rude assertions notwithstanding.DaleSpam doesn't know what he is talking about. Newton's 2nd law is an empirical relation between force and acceleration, it is not a definition although some people do use it as an operational definition of mass. I can measure force and acceleration seperately and Newton's 2nd law tells me the mathematical connection between the two.
Newton observed, as did Galileo (which is why we refer to the principle as Galilean Relativity), that the laws of physics are the same in a boat moving at constant speed on calm seas as they are on land. In other words, the laws of motion are the same for bodies in all inertial reference frames (frames of reference of a body undergoing no change in motion).hey guys i had a doubt can someone please explain me why force=mass x acceleration?