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Re: Causation in Physics: F=ma





"We do not really measure force -- we measure effects we claim to be
caused by force (effects we explain by a construct we call force)."



I suspect this is true of every (physical) measurement. Somewhere in
the dim past I remember reading a short book by "Oppie". In the
appendix he discussed the difference between the whatever and the meter
reading. It was one page length, in French. I have, of course,
forgotten his conclusion.

However, you're forgetting kinesthetic force. Using such common
experience is, I think, very heuristic. I suppose feeling something is
similar to your measurement.

bc

Gary Turner wrote:

We do not really measure force -- we measure effects we claim to be
caused by force (effects we explain by a construct we call force).



This is a very good point. IMHO, the concept of "force" is one that we
have created to help explain why things behave the way they do. It is
certainly not in the realm of fundamentals, such as momentum and energy.

When a system "seeks" a new local minimum in potential energy, elements of
that system will move, possibly changing kinetic energy - and hence
velocity - as a result. The TENDENCY to seek that new level CAUSES the
acceleration, at least in the context that the acceleration is a
consequence of the natural order. That tendency is what we interpret as a
force.

In a way, then, the thing that we call force is what causes the shift on
the energy balance that we measure as acceleration. But does "force"
cause acceleration? I have to go with John on this one - I don't see how
an artificial construct can "cause" a real phenomenon. OTOH, I must also
disagree with John, and venture that causation does not necessarily imply
precedance.

A transfer of energy is responsible for acceleration, but it cannot
possibly precede it. They must be simultaneous.




-- Wolfgang