# Facilitators Discuss Student Pretest Responses

Each week, all TA's (and other tutorial instructors):

1. take the same pretest as the students,
2. analyze student responses on the same pretest,
3. go through the same tutorial the students will do.

TAs go through the physics content, typical student difficulties, and instructional strategies.

In this video, facilitators discuss common responses they see on student pretest responses. Students were asked to draw a free body diagram of a box sliding up an incline (with friction), and a separate free body diagram for the box sliding down the incline. The only forces acting on the box are friction, the normal force from the incline on the box, and gravity. Many students are adding additional forces.

A longer discussion (not placed on the Web due to its length) followed, where they discussed the issues that students were having difficulty with. These issues are also discussed in the second video about TA training that is also available on this Web page.

Actors:
Use following key to figure out who is who:
R = right
L = left
F = front
B = back
Video quality is low due to problems with the videotape. Our apologies.

### Transcript:

LF: I got a lot of people drawing contact forces, for the first free body diagram. They're thinking something, well, if it's sliding up the incline, something must be pushing it up.

RB: Yes, yes, there must be a force if it's going up.

(many voices, unclear)

LB: (French accent, quiet) like the block acts on itself.

RB: Right, right ... maybe someone is pushing it (lots of?) right at the top, it is reversed, though.

RF: Repeatedly I see cases where they have forces balancing up the incline, but coming down the incline it's going down and pushing up when it's going up.

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