With respect to the nature of ideas about force, Max Jammer's book:
Concepts of Force, recently republished by Dover is very interesting. In
light of the ideas there and based on experience in the classroom, it seems
that while most people think of force as cause of velocity and many of us
try to teach force as cause of acceleration instead, when we get right down
to it force is construct. Force is a mental construct we use to explain
motion and the deformation of objects (a kind of motion too). As a
construct then it can be whatever we need it to be to generate fitting,
useful, satisfying explanation, but as construct it does not make the same
sense to worry or argue over which comes first or whether it must be
simultaneous in the same way as we would if we thought of force as cause of
acceleration.
It is interesting to note that 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?). It is also interesting to note that we decided what the
sum of the forces should be rather than "measuring" them all to finally
prove what the sum is.
Dewey
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Dewey I. Dykstra, Jr. Phone: (208)426-3105
Professor of Physics Dept: (208)426-3775
Department of Physics/MCF421/418 Fax: (208)426-4330
Boise State University dykstrad@email.boisestate.edu
1910 University Drive Boise Highlanders
Boise, ID 83725-1570 novice piper: GHB, Uilleann
"As a result of modern research in physics, the ambition and hope,
still cherished by most authorities of the last century, that physical
science could offer a photographic picture and true image of reality
had to be abandoned." --M. Jammer in Concepts of Force, 1957.
"If what we regard as real depends on our theory, how can we make
reality the basis of our philosophy? ...But we cannot distinguish
what is real about the universe without a theory...it makes no sense
to ask if it corresponds to reality, because we do not know what
reality is independent of a theory."--S. Hawking in Black Holes
and Baby Universes, 1993.
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