PHYSICS PROBLEM SOLVING

(^) Example of Group 4B
(^) Group 4B consisted of one woman (KJ) and two male students (LP and JH).
Based on their individual cumulative exam scores at the time of this problem session, this
was a below average group. (z = -.81). All three students were full-time, residential
students at the University. JH was the Recorder. Due to an audio problem, the usable
portion of the videotape began as they were starting the “Plan” section of the problem
solution. However, several portions of the physics description are contained in the
analyzed segment. Students frequently retroactively worked on the physics description.
This group’s free-body diagram was not clearly drawn. Although the tension,
weight of the mug, weight of the sign, and normal vectors are indicated, the diagram is
very cluttered and it is not clear which label is attached to which vector or vector
component (cf. Table 3-10, page 92). This group did not draw idealized, free-body and
force-vector diagrams. This omission hindered their proper identification of the
variables.
In the “Physics Description”, they wrote only one quantitative relationship:
Weight x distance = torque
They neglected to also write Newton’s Second Law. However, in the approach section,
they wrote  F = 0 and   = 0, which of course is a mathematical statement of the basic
principles of statics. They identified target variables  1 and  2. The vector identified as
 1 clearly refers to the tension in the support cable. It is not clear if the other target
variable  2 refers to the normal force or a vertical component of a resultant force at the
point of contact between the strut and the wall.