PHYSICS PROBLEM SOLVING

(^) It could be a reference to the normal force, which, in my experience, some students call a
“weird” force. It could also be a part of an interrupted statement, “And this is a weird
force diagram.” Because the students begin a discussion of specific forces in line 49, I
believe this was a cryptic reference to the normal force.
In line 29, member RM takes over the conversation and indicates the location of
the weight of the bar. This is a new episode for two reasons. First, there is a change of
speaker. Second, now they begin a discussion of a specific force, whereas in the previous
episode, they were talking about all the forces in general. From this discussion of the
weight of the bar, which ends in line 61, they then went on to talk about the weight of the
mug, the normal force, and the tension. In Table 3-3 (page 79) the translation of their
free-body diagram is evident in the force-vector diagram they drew earlier. Thus, in this
transcript segment there are three episodes: In lines 39 to 43 they discuss which
diagrams to include in the Physics Description. The conversation turns to which forces to
include on the free-body diagram in lines 44 to 48. Finally in lines 49 to 61, they discuss
in detail one particular force, the weight of the bar. It is interesting that as they move
from the general to the specific and the discussion becomes more detailed, their episodes
become slightly longer. To summarize, there are two primary cues that a new episode
has begun: (1) a change of thought or topic, and (2) a change of speaker. When these
two cues are both present, the new episode is easiest to define.