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UFM A5 Video Clip 1: The class presents their initial ideas
All groups agree that the stronger force will make the speed increase at a higher rate, but some argue that since the force is constant, the rate of increase will be constant, whereas others refer back to the 'three-track' video they saw in Activity 2 and interpret that to mean the rate of increase decreases. It is notable that students use 'speeding up' and 'slowing down' to describe the rate of change of speed.
UFM A5 Video Clip 3: A group works through the second part of Exploration #1
The group records speed-time data as they use a fan to make the cart decrease in speed, after an initial push. After discussing why the speed decreases, they then reduce the strength of the fan and repeat the experiment. They conclude that in both cases, the speed decreases, but then talk about how the strength of the force affects how quickly this happens. Carol concludes that the stronger the force, the more quickly the speed changes.
UFM A5 Video Clip 5: Two groups continue working on Exploration #2
April and Rose first predict that the cart with more mass will stop first. Then Rose changes her mind and Linda agrees with her, while April tries to clarify the scenario they are considering. Upon seeing that the lower mass cart is the first to stop, they try to rationalize why this is, during which it is evident that they are having some problems with the language needed to describe their thinking. Liz then realizes that the cart with less mass both sped up and slowed down at a faster rate.
UFM A5 Video Clip 6: Two groups consider the final step of Exploration #2
The groups agree that a cart with more mass would need a stronger force to make it increase speed at the same rate as a cart with less mass. Katy then predicts that a cart with three times more mass would need a force that was three times stronger. After their prediction is confirmed by the simulator movie, Katy expresses an appropriate algebraic relationship.
UFM A5 Video Clip 7: Two groups work through Exploration #2 together
The students are surprised by the results of the second experiment, but move on to express the idea that a more massive object needs a stronger force to make its speed change at the same rate as a less massive cart. They express this idea as “the force and the mass have to be the same”, but it is likely they mean the factors multiplying mass and force need to be the same.
UFM A5 Video Clip 8: Group 1 discusses question S3
In discussing their response to question S3, Gail proposes that more mass makes the speed change more quickly. Although the others initially agree with her, Dianne seems to be doubtful, and starts a discussion of the evidence they have seen and what it means. It is again evident that they are having difficulty finding appropriate language to use. Finally, Dianne proposes that more mass means more resistance to change.
UFM A5 Video Clip 9: Group 1 discusses questions S5 and S6
Dianne and Gail initially disagree and again struggle with the language associated with the rate of change of speed. Katie gives a practical example to try to clarify their thinking and they eventually agree on their response. They then use the corresponding relationship in answering question S6, but they are still tentative.
UFM A5 Video Clip 10: A class agrees on their response to question S3
The whole class agrees on the response to a clicker question and then Katie explains her group's thinking in the context of question S4. The instructor asks what observational evidence the class had seen and Erin refers to her group's surprise at the outcome when working with carts of different mass.
UFM A5 Video Clip 12: Some groups present their responses to questions S5 & S6
After a clicker question that shows a consensus in the class, three students describe why they chose to agree with Han. Vicky [off camera] cites some evidence from the activity, but is unsure about the equation. Dawn and Linda then describe how they used Han's equation in two different contexts. Finally, Erin and Faith show how they used Han's equation to answer question S6.
UFM A5 Video Clip 1: The class presents their initial ideas