PHYSICS PROBLEM SOLVING

(^) This first example (Table 3-10, page 92) is at the point where they are
retroactively working on the physics description. What is clear from examining this
diagram and their conversation is that they confused tension in the cable, normally
abbreviated T with torque
. Hence, they write two equations in the “Plan” which they
subsequently solve numerically:

1 ()Wms^31 sin(W.)^5 and

 2 WWms 15  0
They proceed to solve these two equations for the two unknowns and find the answers in
units of newton-meters, which of course is not a unit of force but of torque. ( 1 = 1500
Nm and  2 = -150 Nm) In other words, they find the torques, but not the forces on the
bar, which was the question posed in the problem statement. Although in the dialog seen
in Table 3-10 they say “t”, on their diagram they drew “” which only compounded their
confusion.
Despite some poor physics, Group 4B managed to interact well with one another.
The dialog in Table 3-11 (page 93) illustrates how they request and give clarification of
ideas. The motioning with the pen (Line 105 ff.) serves to visually clarify the idea. Of
the 22 statements in this section, KJ makes 8, JH makes 8 and LP makes 6 statements.
That is, their conversation is well-balanced and all students are participating equally.
Their group functioning is rather good. The reason for this can be seen in the manner in
which they elaborate on ideas. Each student is an equal partner in the solution. Although
there is co-construction of the argument, they are basing the construction on some
erroneous physics, and that resulted in a poorer grade on the problem.