# Facilitators Discuss Possible Student Difficulties

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 how students might misinterpret a free body diagram and thereby make an incorrect prediction for the velocity graph of a fan cart after it has been given an initial push. This issue is contained in the video of student-facilitator interaction that is also available on this Web page.

Actors:
Use following key to figure out who is who:
OF = outside facilitator (off camera)
R = right
L = left
F = front
B = back

### Transcript:

OF: Why was it presented that way, though?

RF: Because the gentle push is an additional initial force.

OF: Okay, and how might the students draw their free body diagram?

RF: They might have another force there for the push.

RB: It says, "draw a free body diagram for the cart-fan system AFTER it is no longer touching your hands.

OF: Right, so is there another force there after it is no longer touching...

RB and RF: No.

RF: But they might still think that.

RB: Right.

LF: the force...

OF: If they think that the force of the hand continues to act on the cart, how would they draw their free body diagram?

RB: They would have an extra (mumble: force?)

LF: there (drawing it on the page)

OF: ...they would have an extra force in there.

RB: Force in addition to the ... in the same direction as the fan.

OF: How would that correspond to their, um, ... how, if at all, would that affect their motion graphs?

RF: If they're thinking about it, as if there's another force, then their velocity should have a greater slope.

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