PHYSICS PROBLEM SOLVING

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many specific and detailed sub-warrants, such as the selection of the point about which to
take the torques.
In a problem involving static equilibrium, the application of Newton’s Second
Law to the situation requires that F = 0. Students (or physicists for that matter) seldom
apply this law and explicitly state “This is valid because of the generally accepted validity
of Newton’s Laws.” Toulmin, I believe, would see physics warrants as unequivocally
supporting a claim:
Warrants are of different kinds, and may confer different degrees of force on the
conclusions they justify. Some warrants authorise us to accept a claim
unequivocally, given the appropriate data--- these warrants entitle us in suitable
cases to qualify our conclusions with the ato make the step from data to conclusion either tentativdverb ‘necessarily’; others authorise us ely, or else subject to
conditions, exceptions, or qualifications--- in these cases other modal qualifiers,
such as ‘probably’ and ‘presumably’, are in place (Toulmin, 1990, pp. 100-101).
It is, however, necessary to support warrants with backings.
In what ways does the backing of warrants differ from the other elements in our
arguments? To begin with the differences between B and W: statements of
warrants, we saw, are hypothetical, bridge-like statements, but the backing for
warrants can be expressed in the form of well as can the data appealed to in direct support of our conclusion (Toulmin, categorical statements of fact quite as
1990, p. 105).
It would, for example, be somewhat unlikely that a physicist would directly or explicitly
state, “categorically,” that Newton’s Laws are valid. When students cite backings, they
may refer to the professor in deference to the teaching assistant or textbook. "That's how
he did it in class," is the simplest example of this type of statement.
In the context of introductory physics problems, there is seldom an opportunity
for "rebuttal" of a claim. A rebuttal is a condition that negates the claim. In this
problem, a rebuttal might be "The sign is not in equilibrium if the tensile strength of the