Re: Causation in Physics: F=ma

[Bob LaMontagne <rlamont@POSTOFFICE.PROVIDENCE.EDU>]

I'm confused - momentum is a time integral of force and energy is a
spatial integral of force. If force is not fundamental, how can momentum
and energy be?

When a ball falls, the decreasing potential energy does not CAUSE the
increase in kinetic energy - their changes are simply associated - at
least I don't see the meaning of the word 'cause' in this situation. I'm
quite a bit more comfortable (in classical physics) with the idea of the
gravitational force causing the ball to accelerate.

Bob at PC

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