UFM A3 Video Clip 1: Group 9 works on STEP 1 of Exploration #1

UFM A3 Video Clip 1: Group 9 works on STEP 1 of Exploration #1

Rachel leads the group in identifying periods when the speed is changing as when a hand was in contact with the cart. Dawn suggests that a 'dramatic' decrease in speed shows a force acting in the opposite direction to the cart's motion.

UFM A3 Video Clip 2: Group 3 works through STEP 3 of Exploration #1

UFM A3 Video Clip 2: Group 3 works through STEP 3 of Exploration #1

The group is initially confused about some details of how the experiment should be performed and the instructor helps them out. Jill realizes that the initial push does not appear on the force-time graph and asks why this is.

UFM A3 Video Clip 3: Group 2 works through STEP 1 of Exploration #2

UFM A3 Video Clip 3: Group 2 works through STEP 1 of Exploration #2

The group discusses their prediction for the speed-time graph of a cart when a fan unit slows it down and then reverses its direction. They agree that the speed will decrease to zero, but there is some discussion about how the speed will behave after the direction is reversed.

UFM A3 Video Clip 4: Group 2 works through STEP 2 of Exploration #2

UFM A3 Video Clip 4: Group 2 works through STEP 2 of Exploration #2

The students run the experiment and then discuss how the speed is behaving at different points in the cart's motion. There seems to be some confusion about which parts of the motion are being addressed.

UFM A3 Video Clip 5: Group 5 works through Exploration #2

UFM A3 Video Clip 5: Group 5 works through Exploration #2

In discussing their prediction in STEP 1, there is some disagreement as to whether the speed has to drop to zero when the direction changes. The experiment provides evidence to support that the cart does stop momentarily. They end by concluding that a decrease in speed is caused by the fan force acting in the opposite direction to the initial push.

UFM A3 Video Clip 6: Group 3 discusses Summarizing Question S2

UFM A3 Video Clip 6: Group 3 discusses Summarizing Question S2

The group discusses what arrows to draw on the diagrams in question S2. It seems that some group members are still not sure about the distinction between the arrows that represent speed and those that represent force.

UFM A3 Video Clip 7: Group 3 discusses Summarizing Question S4

UFM A3 Video Clip 7: Group 3 discusses Summarizing Question S4

The group discusses when the force of the hand is acting on the cart, and so in which of the three diagrams they should show that force. They go back on forth on whether the first two diagrams ('decreasing speed' and 'stopped momentarily') should show the force or not, eventually deciding they both should. However, at this point, they do not think the third diagram ('increasing speed') should show a force.

UFM A3 Video Clip 8: Group 3 continues discussing Summarizing Question S4

UFM A3 Video Clip 8: Group 3 continues discussing Summarizing Question S4

The group continues discussing the three diagrams in question S4. Eventually they argue that it would be reasonable to show the force of the hand in all three diagrams.

UFM A3 Video Clip 9: Three groups present their explanations from S4

UFM A3 Video Clip 9: Three groups present their explanations from S4

Groups 7 and 2 show the backward force of the hand on all three of their diagrams, whereas Group 4 only show it on the middle diagram, when the cart is stopped momentarily. Kathy points out that the question said all three diagrams should have been drawn while the hand was in contact with the cart and Deb seems to agree that, given this, the other group's diagrams make sense.