The group discusses the sections of the graph to highlight and decides that it would be the same sections for both where the hand is in contact and also where the kinetic energy is changing. Anna uses ideas about energy transfers to support this idea.
The instructor has two students come and mark the relevant sections on a speed-time graph sketched on a whiteboard at the front of the class. In this case the whole class agreed with the students' thinking.
The group observes a collision between two carts and Wendy immediately interprets what happened in terms of an energy transfer. In discussing questions about changes in the kinetic energy of the two carts Wendy's comments suggest that she is already thinking in terms of energy transfer and conservation.
The group discusses the speed-time graphs in question S1 and uses the idea that periods of changing speed must be correlated with contact during an interaction. (This is very different from their thinking at the beginning of the previous activity.) In explaining their choices Wendy again draws on ideas about energy transfer.
The group decides that the evidence for a contact push/pull interaction would be a change in speed. Although the question does no ask about energy Wendy reinterprets the question. She justifies her response in terms of energy transfers and changes.