More focused on the Principia,
Home looks further into Newton's justification of the Third Law. Important to
note is what Newton meant when he used the words "action" and
"reaction." By pulling from Opticks,
one would find that Newton is using them in just about the most general terms
that there are. An "action" and "reaction" are not limited
to accelerative forces, but they can be extended to include any situation in
which one thing influences another through some mean.
This raises the interesting notion that we need to be aware
as a teacher or lecturer what our students means when they make a statement. If
Newton describes something in a certain way and allows for a broader definition
than we do, we will miss meaning. The same thing will happen in the classroom.
Home finds that this extension expands Newton's definition
of the Third Law to account for numerous different scenarios, and Newton also
accounted for non-static cases with an early form of a method later attributed
to d'Alembert.
Core to the understanding of the Third Law for Newton was
the Laws of Impact, and these are important to use today as well concerning the
Third Law. Conservation of Momentum is integral to understanding how happens in
a collision, Home holds that the Third Law is not itself an obvious consequence
of the principle of conservation of momentum.
I feel that this can in a way be tied back to the concept of
p-prims. The benefit of the p-prim concept is that they are as far down as you
can reduce a particular concept. That gives a good foundation for moving
forward and advancing understanding so that hopefully, there will be no misunderstandings over
language used to describe situations.
R. W. Home, "The third law in Newton's mechanics," British Journal for the History of Science, Vol. 4, pages 39-51 (1968)
