| Why don't we just agree as follows:
| a) Sometimes ma is calculated from F and sometimes vice versa;
| b) The equation F=ma covers both cases.
In the situation that Mike E. described, see below; is it case (a) or
case (b)?
Or are you saying its either?
_________
| > In my paragraph above (which could benefit from the rest of the
| > context) I specifically am talking about the zero acceleration case
| > where there are multiple forces summing to zero,
|
| Why is that even a question? I have no problem imagining
| that the particle accelerates in the direction of F1, and
| also accelerates in the direction of F2, and also accelerates
| in the direction of
| F3 ... and if the sum of those three accelerations happens to
| be zero, so be it. I don't see why this is any different in
| principle or in practice from the acceleration in an
| epicycloid: it may be that the various contributions to the
| acceleration sum to zero at this-or-that point ... what's the
| big deal? If the accelerations are additive in one
| situation, why are they not additive in another situation?
|
I'm guessing that Mike E. can imagine those a1, a2, and a3's as well;
but he's enquiring as to how to measure them in practice, how would you
measure a1? Or a2? In particular if what you have is data indicating
the position as a function time (say a stroboscopic picture). I would
think the natural thing to measure is simply the overall a (net_a).